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Title: Darwiniana
Author: Thomas Henry Huxley
Release Date: November, 2004 [EBook #6919]
[This file was first posted on February 10, 2003]
Edition: 10
Language: English
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Thomas Henry Huxley
Collected Essays
(1893-1894)
Vol. II
Darwiniana
(Edition: published in 1893)
PREFACE
I have entitled this volume "Darwiniana" because the pieces republished in
it either treat of the ancient doctrine of Evolution, rehabilitated and
placed upon a sound scientific foundation, since and in consequence of, the
publication of the "Origin of Species;" or they attempt to meet the more
weighty of the unsparing criticisms with which that great work was visited
for several years after its appearance; or they record the impression left
by the personality of Mr. Darwin on one who had the privilege and the
happiness of enjoying his friendship for some thirty years; or they
endeavour to sum up his work and indicate its enduring influence on the
course of scientific thought.
Those who take the trouble to read the first two essays, published in 1859
and 1860, will, I think, do me the justice to admit that my zeal to secure
fair play for Mr. Darwin, did not drive me into the position of a mere
advocate; and that, while doing justice to the greatness of the argument I
did not fail to indicate its weak points. I have never seen any reason for
departing from the position which I took up in these two essays; and the
assertion which I sometimes meet with nowadays, that I have "recanted" or
changed my opinions about Mr. Darwin's views, is quite unintelligible to
me.
As I have said in the seventh essay, the fact of evolution is to my mind
sufficiently evidenced by palaeontology; and I remain of the opinion
expressed in the second, that until selective breeding is definitely proved
to give rise to varieties infertile with one another, the logical
foundation of the theory of natural selection is incomplete. We still
remain very much in the dark about the causes of variation; the apparent
inheritance of acquired characters in some cases; and the struggle for
existence within the organism, which probably lies at the bottom of both of
these phenomena.
Some apology is due to the reader for the reproduction of the "Lectures to
Working Men" in their original state. They were taken down in shorthand by
Mr. J. Aldous Mays, who requested me to allow him to print them. I was very
much pressed with work at the time; and, as I could not revise the reports,
which I imagined, moreover, would be of little or no interest to any but my
auditors, I stipulated that a notice should be prefixed to that effect.
This was done; but it did not prevent a considerable diffusion of the
little book in this country and in the United States, nor its translation
into more than one foreign language. Moreover Mr. Darwin often urged me to
revise and expand the lectures into a systematic popular exposition of the
topics of which they treat. I have more than once set about the task: but
the proverb about spoiling a horn and not making a spoon, is particularly
applicable to attempts to remodel a piece of work which may have served its
immediate purpose well enough.
So I have reprinted the lectures as they stand, with all their
imperfections on their heads. It would seem that many people must have
found them useful thirty years ago; and, though the sixties appear now to
be reckoned by many of the rising generation as a part of the dark ages, I
am not without some grounds for suspecting that there yet remains a fair
sprinkling even of "philosophic thinkers" to whom it may be a profitable,
perhaps even a novel, task to descend from the heights of speculation and
go over the A B C of the great biological problem as it was set before a
body of shrewd artisans at that remote epoch.
T. H. H.
Hodeslea, Eastbourne, _April 7th_, 1893.
CONTENTS
I THE DARWINIAN HYPOTHESIS [1859]
II THE ORIGIN OF SPECIES [1860]
III CRITICISM ON "THE ORIGIN OF SPECIES" [1864]
IV THE GENEALOGY OF ANIMALS [1869]
V MR. DARWIN'S CRITICS [1871]
VI EVOLUTION IN BIOLOGY [1878]
VII THE COMING OF AGE OF "THE ORIGIN OF SPECIES" [1880]
VIII CHARLES DARWIN [1882]
IX THE DARWIN MEMORIAL [1885]
X OBITUARY [1888]
XI SIX LECTURES TO WORKING MEN "ON OUR KNOWLEDGE OF THE CAUSES OF THE
PHENOMENA OF ORGANIC NATURE" [1863]
I
THE DARWINIAN HYPOTHESIS
[1859]
The hypothesis of which the present work of Mr. Darwin is but the
preliminary outline, may be stated in his own language as follows:--
"Species originated by means of natural selection, or through the
preservation of the favoured races in the struggle for life." To render
this thesis intelligible, it is necessary to interpret its terms. In the
first place, what is a species? The question is a simple one, but the right
answer to it is hard to find, even if we appeal to those who should know
most about it. It is all those animals or plants which have descended from
a single pair of parents; it is the smallest distinctly definable group of
living organisms; it is an eternal and immutable entity; it is a mere
abstraction of the human intellect having no existence in nature. Such are
a few of the significations attached to this simple word which may be
culled from authoritative sources; and if, leaving terms and theoretical
subtleties aside, we turn to facts and endeavour to gather a meaning for
ourselves, by studying the things to which, in practice, the name of
species is applied, it profits us little. For practice varies as much as
theory. Let two botanists or two zoologists examine and describe the
productions of a country, and one will pretty certainly disagree with the
other as to the number, limits, and definitions of the species into which
he groups the very same things. In these islands, we are in the habit of
regarding mankind as of one species, but a fortnight's steam will land us
in a country where divines and savants, for once in agreement, vie with one
another in loudness of assertion, if not in cogency of proof, that men are
of different species; and, more particularly, that the species negro is so
distinct from our own that the Ten Commandments have actually no reference
to him. Even in the calm region of entomology, where, if anywhere in this
sinful world, passion and prejudice should fail to stir the mind, one
learned coleopterist will fill ten attractive volumes with descriptions of
species of beetles, nine-tenths of which are immediately declared by his
brother beetle-mongers to be no species at all.
The truth is that the number of distinguishable living creatures almost
surpasses imagination. At least 100,000 such kinds of insects alone have
been described and may be identified in collections, and the number of
separable kinds of living things is under-estimated at half a million.
Seeing that most of these obvious kinds have their accidental varieties,
and that they often shade into others by imperceptible degrees, it may well
be imagined that the task of distinguishing between what is permanent and
what fleeting, what is a species and what a mere variety, is sufficiently
formidable.
But is it not possible to apply a test whereby a true species may be known
from a mere variety? Is there no criterion of species? Great authorities
affirm that there is--that the unions of members of the same species are
always fertile, while those of distinct species are either sterile, or
their offspring, called hybrids, are so. It is affirmed not only that this
is an experimental fact, but that it is a provision for the preservation of
the purity of species. Such a criterion as this would be invaluable; but,
unfortunately, not only is it not obvious how to apply it in the great
majority of cases in which its aid is needed, but its general validity is
stoutly denied. The Hon. and Rev. Mr. Herbert, a most trustworthy
authority, not only asserts as the result of his own observations and
experiments that many hybrids are quite as fertile as the parent species,
but he goes so far as to assert that the particular plant _Crinum
capense_ is much more fertile when crossed by a distinct species than
when fertilised by its proper pollen! On the other hand, the famous
Gaertner, though he took the greatest pains to cross the Primrose and the
Cowslip, succeeded only once or twice in several years; and yet it is a
well-established fact that the Primrose and the Cowslip are only varieties
of the same kind of plant. Again, such cases as the following are well
established. The female of species A, if crossed with the male of species
B, is fertile; but, if the female of B is crossed with the male of A, she
remains barren. Facts of this kind destroy the value of the supposed
criterion.
If, weary of the endless difficulties involved in the determination of
species, the investigator, contenting himself with the rough practical
distinction of separable kinds, endeavours to study them as they occur in
nature--to ascertain their relations to the conditions which surround them,
their mutual harmonies and discordancies of structure, the bond of union of
their present and their past history, he finds himself, according to the
received notions, in a mighty maze, and with, at most, the dimmest
adumbration of a plan. If he starts with any one clear conviction, it is
that every part of a living creature is cunningly adapted to some special
use in its life. Has not his Paley told him that that seemingly useless
organ, the spleen, is beautifully adjusted as so much packing between the
other organs? And yet, at the outset of his studies, he finds that no
adaptive reason whatsoever can be given for one-half of the peculiarities
of vegetable structure. He also discovers rudimentary teeth, which are
never used, in the gums of the young calf and in those of the foetal whale;
insects which never bite have rudimental jaws, and others which never fly
have rudimental wings; naturally blind creatures have rudimental eyes; and
the halt have rudimentary limbs. So, again, no animal or plant puts on its
perfect form at once, but all have to start from the same point, however
various the course which each has to pursue. Not only men and horses, and
cats and dogs, lobsters and beetles, periwinkles and mussels, but even the
very sponges and animalcules commence their existence under forms which are
essentially undistinguishable; and this is true of all the infinite variety
of plants. Nay, more, all living beings march, side by side, along the high
road of development, and separate the later the more like they are; like
people leaving church, who all go down the aisle, but having reached the
door, some turn into the parsonage, others go down the village, and others
part only in the next parish. A man in his development runs for a little
while parallel with, though never passing through, the form of the meanest
worm, then travels for a space beside the fish, then journeys along with
the bird and the reptile for his fellow travellers: and only at last, after
a brief companionship with the highest of the four-footed and four-handed
world, rises into the dignity of pure manhood. No competent thinker of the
present day dreams of explaining these indubitable facts by the notion of
the existence of unknown and undiscoverable adaptations to purpose. And we
would remind those who, ignorant of the facts, must be moved by authority,
that no one has asserted the incompetence of the doctrine of final causes,
in its application to physiology and anatomy, more strongly than our own
eminent anatomist, Professor Owen, who, speaking of such cases, says ("On
the Nature of Limbs," pp. 39, 40)--"I think it will be obvious that the
principle of final adaptations fails to satisfy all the conditions of the
problem."
But, if the doctrine of final causes will not help us to comprehend
the anomalies of living structure, the principle of adaptation must
surely lead us to understand why certain living beings are found in
certain regions of the world and not in others. The Palm, as we know,
will not grow in our climate, nor the Oak in Greenland. The white bear
cannot live where the tiger thrives, nor _vice versâ_, and the more
the natural habits of animal and vegetable species are examined, the
more do they seem, on the whole, limited to particular provinces. But
when we look into the facts established by the study of the
geographical distribution of animals and plants it seems utterly
hopeless to attempt to understand the strange and apparently
capricious relations which they exhibit. One would be inclined to
suppose _à priori_ that every country must be naturally peopled by
those animals that are fittest to live and thrive in it. And yet how,
on this hypothesis, are we to account for the absence of cattle in the
Pampas of South America, when those parts of the New World were
discovered? It is not that they were unfit for cattle, for millions of
cattle now run wild there; and the like holds good of Australia and
New Zealand. It is a curious circumstance, in fact, that the animals
and plants of the Northern Hemisphere are not only as well adapted to
live in the Southern Hemisphere as its own autochthones, but are, in
many cases, absolutely better adapted, and so overrun and extirpate
the aborigines. Clearly, therefore, the species which naturally
inhabit a country are not necessarily the best adapted to its climate
and other conditions. The inhabitants of islands are often distinct
from any other known species of animal or plants (witness our recent
examples from the work of Sir Emerson Tennent, on Ceylon), and yet
they have almost always a sort of general family resemblance to the
animals and plants of the nearest mainland. On the other hand, there
is hardly a species of fish, shell, or crab common to the opposite
sides of the narrow isthmus of Panama. [Footnote: See page 60
_Note_.] Wherever we look, then, living nature offers us riddles of
difficult solution, if we suppose that what we see is all that can be
known of it.
But our knowledge of life is not confined to the existing world. Whatever
their minor differences, geologists are agreed as to the vast thickness of
the accumulated strata which compose the visible part of our earth, and the
inconceivable immensity of the time the lapse of which they are the
imperfect but the only accessible witnesses. Now, throughout the greater
part of this long series of stratified rocks are scattered, sometimes very
abundantly, multitudes of organic remains, the fossilised exuviæ of animals
and plants which lived and died while the mud of which the rocks are formed
was yet soft ooze, and could receive and bury them. It would be a great
error to suppose that these organic remains were fragmentary relics. Our
museums exhibit fossil shells of immeasurable antiquity, as perfect as the
day they were formed; whole skeletons without a limb disturbed; nay, the
changed flesh, the developing embryos, and even the very footsteps of
primæval organisms. Thus the naturalist finds in the bowels of the earth
species as well defined as, and in some groups of animals more numerous
than, those which breathe the upper air. But, singularly enough, the
majority of these entombed species are wholly distinct from those that now
live. Nor is this unlikeness without its rule and order. As a broad fact,
the further we go back in time the less the buried species are like
existing forms; and, the further apart the sets of extinct creatures are,
the less they are like one another. In other words, there has been a
regular succession of living beings, each younger set, being in a very
broad and general sense, somewhat more like those which now live.
It was once supposed that this succession had been the result of vast
successive catastrophes, destructions, and re-creations _en masse_;
but catastrophes are now almost eliminated from geological, or at least
palæontological speculation; and it is admitted, on all hands, that the
seeming breaks in the chain of being are not absolute, but only relative to
our imperfect knowledge; that species have replaced species, not in
assemblages, but one by one; and that, if it were possible to have all the
phenomena of the past presented to us, the convenient epochs and formations
of the geologist, though having a certain distinctness, would fade into one
another with limits as undefinable as those of the distinct and yet
separable colours of the solar spectrum.
Such is a brief summary of the main truths which have been established
concerning species. Are these truths ultimate and irresolvable facts, or
are their complexities and perplexities the mere expressions of a higher
law?
A large number of persons practically assume the former position to be
correct. They believe that the writer of the Pentateuch was empowered and
commissioned to teach us scientific as well as other truth, that the
account we find there of the creation of living things is simply and
literally correct, and that anything which seems to contradict it is, by
the nature of the case, false. All the phenomena which have been detailed
are, on this view, the immediate product of a creative fiat and,
consequently, are out of the domain of science altogether.
Whether this view prove ultimately to be true or false, it is, at any rate,
not at present supported by what is commonly regarded as logical proof,
even if it be capable of discussion by reason; and hence we consider
ourselves at liberty to pass it by, and to turn to those views which
profess to rest on a scientific basis only, and therefore admit of being
argued to their consequences. And we do this with the less hesitation as it
so happens that those persons who are practically conversant with the facts
of the case (plainly a considerable advantage) have always thought fit to
range themselves under the latter category.
The majority of these competent persons have up to the present time
maintained two positions--the first, that every species is, within certain
defined limits, fixed and incapable of modification; the second, that every
species was originally produced by a distinct creative act. The second
position is obviously incapable of proof or disproof, the direct operations
of the Creator not being subjects of science; and it must therefore be
regarded as a corollary from the first, the truth or falsehood of which is
a matter of evidence. Most persons imagine that the arguments in favour of
it are overwhelming; but to some few minds, and these, it must be
confessed, intellects of no small power and grasp of knowledge, they have
not brought conviction. Among these minds, that of the famous naturalist
Lamarck, who possessed a greater acquaintance with the lower forms of life
than any man of his day, Cuvier not excepted, and was a good botanist to
boot, occupies a prominent place.
Two facts appear to have strongly affected the course of thought of this
remarkable man--the one, that finer or stronger links of affinity connect
all living beings with one another, and that thus the highest creature
grades by multitudinous steps into the lowest; the other, that an organ may
be developed in particular directions by exerting itself in particular
ways, and that modifications once induced may be transmitted and become
hereditary. Putting these facts together, Lamarck endeavoured to account
for the first by the operation of the second. Place an animal in new
circumstances, says he, and its needs will be altered; the new needs will
create new desires, and the attempt to gratify such desires will result in
an appropriate modification of the organs exerted. Make a man a blacksmith,
and his brachial muscles will develop in accordance with the demands made
upon them, and in like manner, says Lamarck, "the efforts of some
short-necked bird to catch fish without wetting himself have, with time and
perseverance, given rise to all our herons and long-necked waders."
The Lamarckian hypothesis has long since been justly condemned, and it is
the established practice for every tyro to raise his heel against the
carcase of the dead lion. But it is rarely either wise or instructive to
treat even the errors of a really great man with mere ridicule, and in the
present case the logical form of the doctrine stands on a very different
footing from its substance.
If species have really arisen by the operation of natural conditions, we
ought to be able to find those conditions now at work; we ought to be able
to discover in nature some power adequate to modify any given kind of
animal or plant in such a manner as to give rise to another kind, which
would be admitted by naturalists as a distinct species. Lamarck imagined
that he had discovered this _vera causa_ in the admitted facts that
some organs may be modified by exercise; and that modifications, once
produced, are capable of hereditary transmission. It does not seem to have
occurred to him to inquire whether there is any reason to believe that
there are any limits to the amount of modification producible, or to ask
how long an animal is likely to endeavour to gratify an impossible desire.
The bird, in our example, would surely have renounced fish dinners long
before it had produced the least effect on leg or neck.
Since Lamarck's time, almost all competent naturalists have left
speculations on the origin of species to such dreamers as the author of the
"Vestiges," by whose well-intentioned efforts the Lamarckian theory
received its final condemnation in the minds of all sound thinkers.
Notwithstanding this silence, however, the transmutation theory, as it has
been called, has been a "skeleton in the closet" to many an honest
zoologist and botanist who had a soul above the mere naming of dried plants
and skins. Surely, has such an one thought, nature is a mighty and
consistent whole, and the providential order established in the world of
life must, if we could only see it rightly, be consistent with that
dominant over the multiform shapes of brute matter. But what is the history
of astronomy, of all the branches of physics, of chemistry, of medicine,
but a narration of the steps by which the human mind has been compelled,
often sorely against its will, to recognise the operation of secondary
causes in events where ignorance beheld an immediate intervention of a
higher power? And when we know that living things are formed of the same
elements as the inorganic world, that they act and react upon it, bound by
a thousand ties of natural piety, is it probable, nay is it possible, that
they, and they alone, should have no order in their seeming disorder, no
unity in their seeming multiplicity, should suffer no explanation by the
discovery of some central and sublime law of mutual connection?
Questions of this kind have assuredly often arisen, but it might have been
long before they received such expression as would have commanded the
respect and attention of the scientific world, had it not been for the
publication of the work which prompted this article. Its author, Mr.
Darwin, inheritor of a once celebrated name, won his spurs in science when
most of those now distinguished were young men, and has for the last twenty
years held a place in the front ranks of British philosophers. After a
circumnavigatory voyage, undertaken solely for the love of his science, Mr.
Darwin published a series of researches which at once arrested the
attention of naturalists and geologists; his generalisations have since
received ample confirmation and now command universal assent, nor is it
questionable that they have had the most important influence on the
progress of science. More recently Mr. Darwin, with a versatility which is
among the rarest of gifts, turned his attention to a most difficult
question of zoology and minute anatomy; and no living naturalist and
anatomist has published a better monograph than that which resulted from
his labours. Such a man, at all events, has not entered the sanctuary with
unwashed hands, and when he lays before us the results of twenty years'
investigation and reflection we must listen even though we be disposed to
strike. But, in reading his work, it must be confessed that the attention
which might at first be dutifully, soon becomes willingly, given, so clear
is the author's thought, so outspoken his conviction, so honest and fair
the candid expression of his doubts. Those who would judge the book must
read it: we shall endeavour only to make its line of argument and its
philosophical position intelligible to the general reader in our own way.
The Baker Street Bazaar has just been exhibiting its familiar annual
spectacle. Straight-backed, small-headed, big-barrelled oxen, as dissimilar
from any wild species as can well be imagined, contended for attention and
praise with sheep of half-a-dozen different breeds and styes of bloated
preposterous pigs, no more like a wild boar or sow than a city alderman is
like an ourang-outang. The cattle show has been, and perhaps may again be,
succeeded by a poultry show, of whose crowing and clucking prodigies it can
only be certainly predicated that they will be very unlike the aboriginal
_Phasianus gallus._ If the seeker after animal anomalies is not
satisfied, a turn or two in Seven Dials will convince him that the breeds
of pigeons are quite as extraordinary and unlike one another and their
parent stock, while the Horticultural Society will provide him with any
number of corresponding vegetable aberrations from nature's types. He will
learn with no little surprise, too, in the course of his travels, that the
proprietors and producers of these animal and vegetable anomalies regard
them as distinct species, with a firm belief, the strength of which is
exactly proportioned to their ignorance of scientific biology, and which is
the more remarkable as they are all proud of their skill in originating
such "species."
On careful inquiry it is found that all these, and the many other
artificial breeds or races of animals and plants, have been produced by one
method. The breeder--and a skilful one must be a person of much sagacity
and natural or acquired perceptive faculty--notes some slight difference,
arising he knows not how, in some individuals of his stock. If he wish to
perpetuate the difference, to form a breed with the peculiarity in question
strongly marked, he selects such male and female individuals as exhibit the
desired character, and breeds from them. Their offspring are then carefully
examined, and those which exhibit the peculiarity the most distinctly are
selected for breeding; and this operation is repeated until the desired
amount of divergence from the primitive stock is reached. It is then found
that by continuing the process of selection--always breeding, that is, from
well-marked forms, and allowing no impure crosses to interfere--a race may
be formed, the tendency of which to reproduce itself is exceedingly strong;
nor is the limit to the amount of divergence which may be thus produced
known; but one thing is certain, that, if certain breeds of dogs, or of
pigeons, or of horses, were known only in a fossil state, no naturalist
would hesitate in regarding them as distinct species.
But in all these cases we have human interference. Without the breeder
there would be no selection, and without the selection no race. Before
admitting the possibility of natural species having originated in any
similar way, it must be proved that there is in Nature some power which
takes the place of man, and performs a selection _suâ sponte._ It is
the claim of Mr. Darwin that he professes to have discovered the existence
and the _modus operandi_ of this "natural selection," as he terms it;
and, if he be right, the process is perfectly simple and comprehensible,
and irresistibly deducible from very familiar but well nigh forgotten
facts.
Who, for instance, has duly reflected upon all the consequences of the
marvellous struggle for existence which is daily and hourly going on among
living beings? Not only does every animal live at the expense of some other
animal or plant, but the very plants are at war. The ground is full of
seeds that cannot rise into seedlings; the seedlings rob one another of
air, light and water, the strongest robber winning the day, and
extinguishing his competitors. Year after year, the wild animals with which
man never interferes are, on the average, neither more nor less numerous
than they were; and yet we know that the annual produce of every pair is
from one to perhaps a million young; so that it is mathematically certain
that, on the average, as many are killed by natural causes as are born
every year, and those only escape which happen to be a little better fitted
to resist destruction than those which die. The individuals of a species
are like the crew of a foundered ship, and none but good swimmers have a
chance of reaching the land.
Such being unquestionably the necessary conditions under which living
creatures exist, Mr. Darwin discovers in them the instrument of natural
selection. Suppose that in the midst of this incessant competition some
individuals of a species (A) present accidental variations which happen to
fit them a little better than their fellows for the struggle in which they
are engaged, then the chances are in favour, not only of these individuals
being better nourished than the others, but of their predominating over
their fellows in other ways, and of having a better chance of leaving
offspring, which will of course tend to reproduce the peculiarities of
their parents. Their offspring will, by a parity of reasoning, tend to
predominate over their contemporaries, and there being (suppose) no room
for more than one species such as A, the weaker variety will eventually be
destroyed by the new destructive influence which is thrown into the scale,
and the stronger will take its place. Surrounding conditions remaining
unchanged, the new variety (which we may call B)--supposed, for argument's
sake, to be the best adapted for these conditions which can be got out of
the original stock--will remain unchanged, all accidental deviations from
the type becoming at once extinguished, as less fit for their post than B
itself. The tendency of B to persist will grow with its persistence through
successive generations, and it will acquire all the characters of a new
species.
But, on the other hand, if the conditions of life change in any degree,
however slight, B may no longer be that form which is best adapted to
withstand their destructive, and profit by their sustaining, influence; in
which case if it should give rise to a more competent variety (C), this
will take its place and become a new species; and thus, by natural
selection, the species B and C will be successively derived from A.
That this most ingenious hypothesis enables us to give a reason for many
apparent anomalies in the distribution of living beings in time and space,
and that it is not contradicted by the main phenomena of life and
organisation appear to us to be unquestionable; and, so far, it must be
admitted to have an immense advantage over any of its predecessors. But it
is quite another matter to affirm absolutely either the truth or falsehood
of Mr. Darwin's views at the present stage of the inquiry. Goethe has an
excellent aphorism defining that state of mind which he calls "Thätige
Skepsis"--active doubt. It is doubt which so loves truth that it neither
dares rest in doubting, nor extinguish itself by unjustified belief; and we
commend this state of mind to students of species, with respect to Mr.
Darwin's or any other hypothesis, as to their origin. The combined
investigations of another twenty years may, perhaps, enable naturalists to
say whether the modifying causes and the selective power, which Mr. Darwin
has satisfactorily shown to exist in Nature, are competent to produce all
the effects he ascribes to them; or whether, on the other hand, he has been
led to over-estimate the value of the principle of natural selection, as
greatly as Lamarck over-estimated his _vera causa_ of modification by
exercise.
But there is, at all events, one advantage possessed by the more recent
writer over his predecessor. Mr. Darwin abhors mere speculation as nature
abhors a vacuum. He is as greedy of cases and precedents as any
constitutional lawyer, and all the principles he lays down are capable of
being brought to the test of observation and experiment. The path he bids
us follow professes to be, not a mere airy track, fabricated of ideal
cobwebs, but a solid and broad bridge of facts. If it be so, it will carry
us safely over many a chasm in our knowledge, and lead us to a region free
from the snares of those fascinating but barren virgins, the Final Causes,
against whom a high authority has so justly warned us. "My sons, dig in the
vineyard," were the last words of the old man in the fable: and, though the
sons found no treasure, they made their fortunes by the grapes.
II
THE ORIGIN OF SPECIES
[1860]
Mr. Darwin's long-standing and well-earned scientific eminence probably
renders him indifferent to that social notoriety which passes by the name
of success; but if the calm spirit of the philosopher have not yet wholly
superseded the ambition and the vanity of the carnal man within him, he
must be well satisfied with the results of his venture in publishing the
"Origin of Species." Overflowing the narrow bounds of purely scientific
circles, the "species question" divides with Italy and the Volunteers the
attention of general society. Everybody has read Mr. Darwin's book, or, at
least, has given an opinion upon its merits or demerits; pietists, whether
lay or ecclesiastic, decry it with the mild railing which sounds so
charitable; bigots denounce it with ignorant invective; old ladies of both
sexes consider it a decidedly dangerous book, and even savants, who have no
better mud to throw, quote antiquated writers to show that its author is no
better than an ape himself; while every philosophical thinker hails it as a
veritable Whitworth gun in the armoury of liberalism; and all competent
naturalists and physiologists, whatever their opinions as to the ultimate
fate of the doctrines put forth, acknowledge that the work in which they
are embodied is a solid contribution to knowledge and inaugurates a new
epoch in natural history.
Nor has the discussion of the subject been restrained within the limits of
conversation. When the public is eager and interested, reviewers must
minister to its wants; and the genuine _littérateur_ is too much in
the habit of acquiring his knowledge from the book he judges--as the
Abyssinian is said to provide himself with steaks from the ox which carries
him--to be withheld from criticism of a profound scientific work by the
mere want of the requisite preliminary scientific acquirement; while, on
the other hand, the men of science who wish well to the new views, no less
than those who dispute their validity, have naturally sought opportunities
of expressing their opinions. Hence it is not surprising that almost all
the critical journals have noticed Mr. Darwin's work at greater or less
length; and so many disquisitions, of every degree of excellence, from the
poor product of ignorance, too often stimulated by prejudice, to the fair
and thoughtful essay of the candid student of Nature, have appeared, that
it seems an almost hopeless task to attempt to say anything new upon the
question.
But it may be doubted if the knowledge and acumen of prejudged scientific
opponents, and the subtlety of orthodox special pleaders, have yet exerted
their full force in mystifying the real issues of the great controversy
which has been set afoot, and whose end is hardly likely to be seen by this
generation; so that, at this eleventh hour, and even failing anything new,
it may be useful to state afresh that which is true, and to put the
fundamental positions advocated by Mr. Darwin in such a form that they may
be grasped by those whose special studies lie in other directions. And the
adoption of this course may be the more advisable, because, notwithstanding
its great deserts, and indeed partly on account of them, the "Origin of
Species" is by no means an easy book to read--if by reading is implied the
full comprehension of an author's meaning.
We do not speak jestingly in saying that it is Mr. Darwin's misfortune to
know more about the question he has taken up than any man living.
Personally and practically exercised in zoology, in minute anatomy, in
geology; a student of geographical distribution, not on maps and in museums
only, but by long voyages and laborious collection; having largely advanced
each of these branches of science, and having spent many years in gathering
and sifting materials for his present work, the store of accurately
registered facts upon which the author of the "Origin of Species" is able
to draw at will is prodigious.
But this very superabundance of matter must have been embarrassing to a
writer who, for the present, can only put forward an abstract of his views;
and thence it arises, perhaps, that notwithstanding the clearness of the
style, those who attempt fairly to digest the book find much of it a sort
of intellectual pemmican--a mass of facts crushed and pounded into shape,
rather than held together by the ordinary medium of an obvious logical
bond; due attention will, without doubt, discover this bond, but it is
often hard to find.
Again, from sheer want of room, much has to be taken for granted which
might readily enough be proved; and hence, while the adept, who can supply
the missing links in the evidence from his own knowledge, discovers fresh
proof of the singular thoroughness with which all difficulties have been
considered and all unjustifiable suppositions avoided, at every reperusal
of Mr. Darwin's pregnant paragraphs, the novice in biology is apt to
complain of the frequency of what he fancies is gratuitous assumption.
Thus while it may be doubted if, for some years, any one is likely to be
competent to pronounce judgment on all the issues raised by Mr. Darwin,
there is assuredly abundant room for him, who, assuming the humbler, though
perhaps as useful, office of an interpreter between the "Origin of Species"
and the public, contents himself with endeavouring to point out the nature
of the problems which it discusses; to distinguish between the ascertained
facts and the theoretical views which it contains; and finally, to show the
extent to which the explanation it offers satisfies the requirements of
scientific logic. At any rate, it is this office which we purpose to
undertake in the following pages.
It may be safely assumed that our readers have a general conception of the
nature of the objects to which the word "species" is applied; but it has,
perhaps, occurred to a few, even to those who are naturalists _ex
professo_, to reflect, that, as commonly employed, the term has a double
sense and denotes two very different orders of relations. When we call a
group of animals, or of plants, a species, we may imply thereby, either
that all these animals or plants have some common peculiarity of form or
structure; or, we may mean that they possess some common functional
character. That part of biological science which deals with form and
structure is called Morphology--that which concerns itself with function,
Physiology--so that we may conveniently speak of these two senses, or
aspects, of "species"--the one as morphological, the other as
physiological. Regarded from the former point of view, a species is nothing
more than a kind of animal or plant, which is distinctly definable from all
others, by certain constant, and not merely sexual, morphological
peculiarities. Thus horses form a species, because the group of animals to
which that name is applied is distinguished from all others in the world by
the following constantly associated characters. They have--1, A vertebral
column; 2, Mammae; 3, A placental embryo; 4, Four legs; 5, A single
well-developed toe in each foot provided with a hoof; 6, A bushy tail; and
7, Callosities on the inner sides of both the fore and the hind legs. The
asses, again, form a distinct species, because, with the same characters,
as far as the fifth in the above list, all asses have tufted tails, and
have callosities only on the inner side of the fore-legs. If animals were
discovered having the general characters of the horse, but sometimes with
callosities only on the fore-legs, and more or less tufted tails; or
animals having the general characters of the ass, but with more or less
bushy tails, and sometimes with callosities on both pairs of legs, besides
being intermediate in other respects--the two species would have to be
merged into one. They could no longer be regarded as morphologically
distinct species, for they would not be distinctly definable one from the
other.
However bare and simple this definition of species may appear to be, we
confidently appeal to all practical naturalists, whether zoologists,
botanists, or palaeontologists, to say if, in the vast majority of cases,
they know, or mean to affirm, anything more of the group of animals or
plants they so denominate than what has just been stated. Even the most
decided advocates of the received doctrines respecting species admit this.
"I apprehend," says Professor Owen, [Footnote: "On the Osteology of the
Chimpanzees and Orangs"; _Transactions of the Zoological Society_,
1858.] "that few naturalists nowadays, in describing and proposing a name
for what they call 'a new _species_,' use that term to signify what
was meant by it twenty or thirty years ago; that is, an originally distinct
creation, maintaining its primitive distinction by obstructive generative
peculiarities. The proposer of the new species now intends to state no more
than he actually knows; as, for example, that the differences on which he
founds the specific character are constant in individuals of both sexes, so
far as observation has reached; and that they are not due to domestication
or to artificially superinduced external circumstances, or to any outward
influence within his cognizance; that the species is wild, or is such as it
appears by Nature."
If we consider, in fact, that by far the largest proportion of recorded
existing species are known only by the study of their skins, or bones, or
other lifeless exuviae; that we are acquainted with none, or next to none,
of their physiological peculiarities, beyond those which can be deduced
from their structure, or are open to cursory observation; and that we
cannot hope to learn more of any of those extinct forms of life which now
constitute no inconsiderable proportion of the known Flora and Fauna of the
world: it is obvious that the definitions of these species can be only of a
purely structural, or morphological, character. It is probable that
naturalists would have avoided much confusion of ideas if they had more
frequently borne the necessary limitations of our knowledge in mind. But
while it may safely be admitted that we are acquainted with only the
morphological characters of the vast majority of species--the functional or
physiological, peculiarities of a few have been carefully investigated, and
the result of that study forms a large and most interesting portion of the
physiology of reproduction.
The student of Nature wonders the more and is astonished the less, the more
conversant he becomes with her operations; but of all the perennial
miracles she offers to his inspection, perhaps the most worthy of
admiration is the development of a plant or of an animal from its embryo.
Examine the recently laid egg of some common animal, such as a salamander
or newt. It is a minute spheroid in which the best microscope will reveal
nothing but a structureless sac, enclosing a glairy fluid, holding granules
in suspension. [Footnote: When this sentence was written, it was generally
believed that the original nucleus of the egg (the germinal vesicle)
disappeared. 1893.] But strange possibilities lie dormant in that
semi-fluid globule. Let a moderate supply of warmth reach its watery
cradle, and the plastic matter undergoes changes so rapid, yet so steady
and purposelike in their succession, that one can only compare them to
those operated by a skilled modeller upon a formless lump of clay. As with
an invisible trowel, the mass is divided and subdivided into smaller and
smaller portions, until it is reduced to an aggregation of granules not too
large to build withal the finest fabrics of the nascent organism. And,
then, it is as if a delicate finger traced out the line to be occupied by
the spinal column, and moulded the contour of the body; pinching up the
head at one end, the tail at the other, and fashioning flank and limb into
due salamandrine proportions, in so artistic a way, that, after watching
the process hour by hour, one is almost involuntarily possessed by the
notion, that some more subtle aid to vision than an achromatic, would show
the hidden artist, with his plan before him, striving with skilful
manipulation to perfect his work.
As life advances, and the young amphibian ranges the waters, the terror of
his insect contemporaries, not only are the nutritious particles supplied
by its prey, by the addition of which to its frame, growth takes place,
laid down, each in its proper spot, and in such due proportion to the rest,
as to reproduce the form, the colour, and the size, characteristic of the
parental stock; but even the wonderful powers of reproducing lost parts
possessed by these animals are controlled by the same governing tendency.
Cut off the legs, the tail, the jaws, separately or all together, and, as
Spallanzani showed long ago, these parts not only grow again, but the
redintegrated limb is formed on the same type as those which were lost. The
new jaw, or leg, is a newt's, and never by any accident more like that of a
frog. What is true of the newt is true of every animal and of every plant;
the acorn tends to build itself up again into a woodland giant such as that
from whose twig it fell; the spore of the humblest lichen reproduces the
green or brown incrustation which gave it birth; and at the other end of
the scale of life, the child that resembled neither the paternal nor the
maternal side of the house would be regarded as a kind of monster.
So that the one end to which, in all living beings, the formative impulse
is tending--the one scheme which the Archæus of the old speculators strives
to carry out, seems to be to mould the offspring into the likeness of the
parent. It is the first great law of reproduction, that the offspring tends
to resemble its parent or parents, more closely than anything else.
Science will some day show us how this law is a necessary consequence of
the more general laws which govern matter; but, for the present, more can
hardly be said than that it appears to be in harmony with them. We know
that the phænomena of vitality are not something apart from other physical
phænomena, but one with them; and matter and force are the two names of the
one artist who fashions the living as well as the lifeless. Hence living
bodies should obey the same great laws as other matter--nor, throughout
Nature, is there a law of wider application than this, that a body impelled
by two forces takes the direction of their resultant. But living bodies may
be regarded as nothing but extremely complex bundles of forces held in a
mass of matter, as the complex forces of a magnet are held in the steel by
its coercive force; and, since the differences of sex are comparatively
slight, or, in other words, the sum of the forces in each has a very
similar tendency, their resultant, the offspring, may reasonably be
expected to deviate but little from a course parallel to either, or to
both.
Represent the reason of the law to ourselves by what physical metaphor or
analogy we will, however, the great matter is to apprehend its existence
and the importance of the consequences deducible from it. For things which
are like to the same are like to one another; and if, in a great series of
generations, every offspring is like its parent, it follows that all the
offspring and all the parents must be like one another; and that, given an
original parental stock, with the opportunity of undisturbed
multiplication, the law in question necessitates the production, in course
of time, of an indefinitely large group, the whole of the members of which
are at once very similar and are blood relations, having descended from the
same parent, or pair of parents. The proof that all the members of any
given group of animals, or plants, had thus descended, would be ordinarily
considered sufficient to entitle them to the rank of physiological species,
for most physiologists consider species to be definable as "the offspring
of a single primitive stock."
But though it is quite true that all those groups we call species
_may_, according to the known laws of reproduction, have descended
from a single stock, and though it is very likely they really have done so,
yet this conclusion rests on deduction and can hardly hope to establish
itself upon a basis of observation. And the primitiveness of the supposed
single stock, which, after all, is the essential part of the matter, is not
only a hypothesis, but one which has not a shadow of foundation, if by
"primitive" be meant "independent of any other living being." A scientific
definition, of which an unwarrantable hypothesis forms an essential part,
carries its condemnation within itself; but, even supposing such a
definition were, in form, tenable, the physiologist who should attempt to
apply it in Nature would soon find himself involved in great, if not
inextricable, difficulties. As we have said, it is indubitable that
offspring _tend_ to resemble the parental organism, but it is equally
true that the similarity attained never amounts to identity either in form
or in structure. There is always a certain amount of deviation, not only
from the precise characters of a single parent, but when, as in most
animals and many plants, the sexes are lodged in distinct individuals, from
an exact mean between the two parents. And indeed, on general principles,
this slight deviation seems as intelligible as the general similarity, if
we reflect how complex the co-operating "bundles of forces" are, and how
improbable it is that, in any case, their true resultant shall coincide
with any mean between the more obvious characters of the two parents.
Whatever be its cause, however, the co-existence of this tendency to minor
variation with the tendency to general similarity, is of vast importance in
its bearing on the question of the origin of species.
As a general rule, the extent to which an offspring differs from its parent
is slight enough; but, occasionally, the amount of difference is much more
strongly marked, and then the divergent offspring receives the name of a
Variety. Multitudes, of what there is every reason to believe are such
varieties, are known, but the origin of very few has been accurately
recorded, and of these we will select two as more especially illustrative
of the main features of variation. The first of them is that of the "Ancon"
or "Otter" sheep, of which a careful account is given by Colonel David
Humphreys, F.R.S., in a letter to Sir Joseph Banks, published in the
"Philosophical Transactions" for 1813. It appears that one Seth Wright, the
proprietor of a farm on the banks of the Charles River, in Massachusetts,
possessed a flock of fifteen ewes and a ram of the ordinary kind. In the
year 1791, one of the ewes presented her owner with a male lamb, differing,
for no assignable reason, from its parents by a proportionally long body
and short bandy legs, whence it was unable to emulate its relatives in
those sportive leaps over the neighbours' fences, in which they were in the
habit of indulging, much to the good farmer's vexation.
The second case is that detailed by a no less unexceptionable authority
than Réaumur, in his "Art de faire éclore les Poulets." A Maltese couple,
named Kelleia, whose hands and feet were constructed upon the ordinary
human model, had born to them a son, Gratio, who possessed six perfectly
movable fingers on each hand, and six toes, not quite so well formed, on
each foot. No cause could be assigned for the appearance of this unusual
variety of the human species.
Two circumstances are well worthy of remark in both these cases. In each,
the variety appears to have arisen in full force, and, as it were, _per
saltum_; a wide and definite difference appearing, at once, between the
Ancon ram and the ordinary sheep; between the six-fingered and six-toed
Gratio Kelleia and ordinary men. In neither case is it possible to point
out any obvious reason for the appearance of the variety. Doubtless there
were determining causes for these as for all other phenomena; but they do
not appear, and we can be tolerably certain that what are ordinarily
understood as changes in physical conditions, as in climate, in food, or
the like, did not take place and had nothing to do with the matter. It was
no case of what is commonly called adaptation to circumstances; but, to use
a conveniently erroneous phrase, the variations arose spontaneously. The
fruitless search after final causes leads their pursuers a long way; but
even those hardy teleologists, who are ready to break through all the laws
of physics in chase of their favourite will-o'-the-wisp, may be puzzled to
discover what purpose could be attained by the stunted legs of Seth
Wright's ram or the hexadactyle members of Gratio Kelleia.
Varieties then arise we know not why; and it is more than probable that the
majority of varieties have arisen in this "spontaneous" manner, though we
are, of course, far from denying that they may be traced, in some cases, to
distinct external influences; which are assuredly competent to alter the
character of the tegumentary covering, to change colour, to increase or
diminish the size of muscles, to modify constitution, and, among plants, to
give rise to the metamorphosis of stamens into petals, and so forth. But
however they may have arisen, what especially interests us at present is,
to remark that, once in existence, many varieties obey the fundamental law
of reproduction that like tends to produce like; and their offspring
exemplify it by tending to exhibit the same deviation from the parental
stock as themselves. Indeed, there seems to be, in many instances, a
prepotent influence about a newly-arisen variety which gives it what one
may call an unfair advantage over the normal descendants from the same
stock. This is strikingly exemplified by the case of Gratio Kelleia, who
married a woman with the ordinary pentadactyle extremities, and had by her
four children, Salvator, George, André, and Marie. Of these children
Salvator, the eldest boy, had six fingers and six toes, like his father;
the second and third, also boys, had five fingers and five toes, like their
mother, though the hands and feet of George were slightly deformed. The
last, a girl, had five fingers and five toes, but the thumbs were slightly
deformed. The variety thus reproduced itself purely in the eldest, while
the normal type reproduced itself purely in the third, and almost purely in
the second and last: so that it would seem, at first, as if the normal type
were more powerful than the variety. But all these children grew up and
intermarried with normal wives and husband, and then, note what took place:
Salvator had four children, three of whom exhibited the hexadactyle members
of their grandfather and father, while the youngest had the pentadactyle
limbs of the mother and grandmother; so that here, notwithstanding a double
pentadactyle dilution of the blood, the hexadactyle variety had the best of
it. The same pre-potency of the variety was still more markedly exemplified
in the progeny of two of the other children, Marie and George. Marie (whose
thumbs only were deformed) gave birth to a boy with six toes, and three
other normally formed children; but George, who was not quite so pure a
pentadactyle, begot, first, two girls, each of whom had six fingers and
toes; then a girl with six fingers on each hand and six toes on the right
foot, but only five toes on the left; and lastly, a boy with only five
fingers and toes. In these instances, therefore, the variety, as it were,
leaped over one generation to reproduce itself in full force in the next.
Finally, the purely pentadactyle André was the father of many children, not
one of whom departed from the normal parental type.
If a variation which approaches the nature of a monstrosity can strive thus
forcibly to reproduce itself, it is not wonderful that less aberrant
modifications should tend to be preserved even more strongly; and the
history of the Ancon sheep is, in this respect, particularly instructive.
With the "'cuteness" characteristic of their nation, the neighbours of the
Massachusetts farmer imagined it would be an excellent thing if all his
sheep were imbued with the stay-at-home tendencies enforced by Nature upon
the newly-arrived ram; and they advised Wright to kill the old patriarch of
his fold, and install the Ancon ram in his place. The result justified
their sagacious anticipations, and coincided very nearly with what occurred
to the progeny of Gratio Kelleia. The young lambs were almost always either
pure Ancons, or pure ordinary sheep.[Footnote: Colonel Humphreys'
statements are exceedingly explicit on this point:--. "When an Ancon ewe is
impregnated by a common ram, the increase resembles wholly either the ewe
or the ram. The increase of the common ewe impregnated by an Ancon ram
follows entirely the one or the other, without blending any of the
distinguishing and essential peculiarities of both. Frequent instances have
happened where common ewes have had twins by Ancon rams, when one exhibited
the complete marks and features of the ewe, the other of the ram. The
contrast has been rendered singularly striking, when one short-legged and
one long-legged lamb, produced at a birth, have been seen sucking the dam
at the same time."--_Philosophical Transactions_, 1813, Ft. I. pp. 89,
90.] But when sufficient Ancon sheep were obtained to interbreed with one
another, it was found that the offspring was always pure Ancon. Colonel
Humphreys, in fact, states that he was acquainted with only "one
questionable case of a contrary nature." Here, then, is a remarkable and
well-established instance, not only of a very distinct race being
established _per saltum_, but of that race breeding "true" at once,
and showing no mixed forms, even when crossed with another breed.
By taking care to select Ancons of both sexes, for breeding from, it thus
became easy to establish an extremely well-marked race; so peculiar that,
even when herded with other sheep, it was noted that the Ancons kept
together. And there is every reason to believe that the existence of this
breed might have been indefinitely protracted; but the introduction of the
Merino sheep, which were not only very superior to the Ancons in wool and
meat, but quite as quiet and orderly, led to the complete neglect of the
new breed, so that, in 1813, Colonel Humphreys found it difficult to obtain
the specimen, the skeleton of which was presented to Sir Joseph Banks. We
believe that, for many years, no remnant of it has existed in the United
States.
Gratio Kelleia was not the progenitor of a race of six-fingered men, as
Seth Wright's ram became a nation of Ancon sheep, though the tendency of
the variety to perpetuate itself appears to have been fully as strong in
the one case as in the other. And the reason of the difference is not far
to seek. Seth Wright took care not to weaken the Ancon blood by matching
his Ancon ewes with any but males of the same variety, while Gratio
Kelleia's sons were too far removed from the patriarchal times to
intermarry with their sisters; and his grand-children seem not to have been
attracted by their six-fingered cousins. In other words, in the one example
a race was produced, because, for several generations, care was taken to
_select_ both parents of the breeding stock from animals exhibiting a
tendency to vary in the same direction; while, in the other, no race was
evolved, because no such selection was exercised. A race is a propagated
variety; and as, by the laws of reproduction, offspring tend to assume the
parental forms, they will be more likely to propagate a variation exhibited
by both parents than that possessed by only one.
There is no organ of the body of an animal which may not, and does not,
occasionally, vary more or less from the normal type; and there is no
variation which may not be transmitted and which, if selectively
transmitted, may not become the foundation of a race. This great truth,
sometimes forgotten by philosophers, has long been familiar to practical
agriculturists and breeders; and upon it rest all the methods of improving
the breeds of domestic animals, which, for the last century, have been
followed with so much success in England. Colour, form, size, texture of
hair or wool, proportions of various parts, strength or weakness of
constitution, tendency to fatten or to remain lean, to give much or little
milk, speed, strength, temper, intelligence, special instincts; there is
not one of these characters the transmission of which is not an every-day
occurrence within the experience of cattle-breeders, stock-farmers,
horse-dealers, and dog and poultry fanciers. Nay, it is only the other day
that an eminent physiologist, Dr. Brown-Séquard, communicated to the Royal
Society his discovery that epilepsy, artificially produced in guinea-pigs,
by a means which he has discovered, is transmitted to their offspring.
[Footnote: Compare Weismann's _Essays Upon Heredity_, p. 310, _et
seq_. 1893.]
But a race, once produced, is no more a fixed and immutable entity than the
stock whence it sprang; variations arise among its members, and as these
variations are transmitted like any others, new races may be developed out
of the pre-existing one _ad infinitum_, or, at least, within any limit
at present determined. Given sufficient time and sufficiently careful
selection, and the multitude of races which may arise from a common stock
is as astonishing as are the extreme structural differences which they may
present. A remarkable example of this is to be found in the rock-pigeon,
which Mr. Darwin has, in our opinion, satisfactorily demonstrated to be the
progenitor of all our domestic pigeons, of which there are certainly more
than a hundred well-marked races. The most noteworthy of these races are,
the four great stocks known to the "fancy" as tumblers, pouters, carriers,
and fantails; birds which not only differ most singularly in size, colour,
and habits, but in the form of the beak and of the skull; in the
proportions of the beak to the skull; in the number of tail-feathers; in
the absolute and relative size of the feet; in the presence or absence of
the uropygial gland; in the number of vertebræ in the back; in short, in
precisely those characters in which the genera and species of birds differ
from one another.
And it is most remarkable and instructive to observe, that none of these
races can be shown to have been originated by the action of changes in what
are commonly called external circumstances, upon the wild rock-pigeon. On
the contrary, from time immemorial pigeon-fanciers have had essentially
similar methods of treating their pets, which have been housed, fed,
protected and cared for in much the same way in all pigeonries. In fact,
there is no case better adapted than that of the pigeons to refute the
doctrine which one sees put forth on high authority, that "no other
characters than those founded on the development of bone for the attachment
of muscles" are capable of variation. In precise contradiction of this
hasty assertion, Mr. Darwin's researches prove that the skeleton of the
wings in domestic pigeons has hardly varied at all from that of the wild
type; while, on the other hand, it is in exactly those respects, such as
the relative length of the beak and skull, the number of the vertebrae, and
the number of the tail-feathers, in which muscular exertion can have no
important influence, that the utmost amount of variation has taken place.
We have said that the following out of the properties exhibited by
physiological species would lead us into difficulties, and at this point
they begin to be obvious; for if, as the result of spontaneous variation
and of selective breeding, the progeny of a common stock may become
separated into groups distinguished from one another by constant, not
sexual, morphological characters, it is clear that the physiological
definition of species is likely to clash with the morphological definition.
No one would hesitate to describe the pouter and the tumbler as distinct
species, if they were found fossil, or if their skins and skeletons were
imported, as those of exotic wild birds commonly are--and without doubt, if
considered alone, they are good and distinct morphological species. On the
other hand, they are not physiological species, for they are descended from
a common stock, the rock-pigeon.
Under these circumstances, as it is admitted on all sides that races occur
in Nature, how are we to know whether any apparently distinct animals are
really of different physiological species, or not, seeing that the amount
of morphological difference is no safe guide? Is there any test of a
physiological species? The usual answer of physiologists is in the
affirmative. It is said that such a test is to be found in the phænomena of
hybridisation--in the results of crossing races, as compared with the
results of crossing species.
So far as the evidence goes at present, individuals, of what are certainly
known to be mere races produced by selection, however distinct they may
appear to be, not only breed freely together, but the offspring of such
crossed races are perfectly fertile with one another. Thus, the spaniel and
the greyhound, the dray-horse and the Arab, the pouter and the tumbler,
breed together with perfect freedom, and their mongrels, if matched with
other mongrels of the same kind, are equally fertile.
On the other hand, there can be no doubt that the individuals of many
natural species are either absolutely infertile if crossed with individuals
of other species, or, if they give rise to hybrid offspring, the hybrids so
produced are infertile when paired together. The horse and the ass, for
instance, if so crossed, give rise to the mule, and there is no certain
evidence of offspring ever having been produced by a male and female mule.
The unions of the rock-pigeon and the ring-pigeon appear to be equally
barren of result. Here, then, says the physiologist, we have a means of
distinguishing any two true species from any two varieties. If a male and a
female, selected from each group, produce offspring, and that offspring is
fertile with others produced in the same way, the groups are races and not
species. If, on the other hand, no result ensues, or if the offspring are
infertile with others produced in the same way, they are true physiological
species. The test would be an admirable one, if, in the first place, it
were always practicable to apply it, and if, in the second, it always
yielded results susceptible of a definite interpretation. Unfortunately, in
the great majority of cases, this touchstone for species is wholly
inapplicable.
The constitution of many wild animals is so altered by confinement that
they will not breed even with their own females, so that the negative
results obtained from crosses are of no value; and the antipathy of wild
animals of different species for one another, or even of wild and tame
members of the same species, is ordinarily so great, that it is hopeless to
look for such unions in Nature. The hermaphrodism of most plants, the
difficulty in the way of insuring the absence of their own or the proper
working of other pollen, are obstacles of no less magnitude in applying the
test to them. And, in both animals and plants, is super-added the further
difficulty, that experiments must be continued over a long time for the
purpose of ascertaining the fertility of the mongrel or hybrid progeny, as
well as of the first crosses from which they spring.
Not only do these great practical difficulties lie in the way of applying
the hybridisation test, but even when this oracle can be questioned, its
replies are sometimes as doubtful as those of Delphi. For example, cases
are cited by Mr. Darwin, of plants which are more fertile with the pollen
of another species than with their own; and there are others, such as
certain _Fuci,_ the male element of which will fertilise the ovule of
a plant of distinct species, while the males of the latter species are
ineffective with the females of the first. So that, in the last-named
instance, a physiologist, who should cross the two species in one way,
would decide that they were true species; while another, who should cross
them in the reverse way, would, with equal justice, according to the rule,
pronounce them to be mere races. Several plants, which there is great
reason to believe are mere varieties, are almost sterile when crossed;
while both animals and plants, which have always been regarded by
naturalists as of distinct species, turn out, when the test is applied, to
be perfectly fertile. Again, the sterility or fertility of crosses seems to
bear no relation to the structural resemblances or differences of the
members of any two groups.
Mr. Darwin has discussed this question with singular ability and
circumspection, and his conclusions are summed up as follows, at page 276
of his work:--
"First crosses between forms sufficiently distinct to be ranked as species,
and their hybrids, are very generally, but not universally, sterile. The
sterility is of all degrees, and is often so slight that the two most
careful experimentalists who have ever lived have come to diametrically
opposite conclusions in ranking forms by this test. The sterility is
innately variable in individuals of the same species, and is eminently
susceptible of favourable and unfavourable conditions. The degree of
sterility does not strictly follow systematic affinity, but is governed by
several curious and complex laws. It is generally different and sometimes
widely different, in reciprocal crosses between the same two species. It is
not always equal in degree in a first cross, and in the hybrid produced
from this cross.
"In the same manner as in grafting trees, the capacity of one species or
variety to take on another is incidental on generally unknown differences
in their vegetative systems; so in crossing, the greater or less facility
of one species to unite with another is incidental on unknown differences
in their reproductive systems. There is no more reason to think that
species have been specially endowed with various degrees of sterility to
prevent them crossing and breeding in Nature, than to think that trees have
been specially endowed with various and somewhat analogous degrees of
difficulty in being grafted together, in order to prevent them becoming
inarched in our forests.
"The sterility of first crosses between pure species, which have their
reproductive systems perfect, seems to depend on several circumstances; in
some cases largely on the early death of the embryo. The sterility of
hybrids which have their reproductive systems imperfect, and which have had
this system and their whole organisation disturbed by being compounded of
two distinct species, seems closely allied to that sterility which so
frequently affects pure species when their natural conditions of life have
been disturbed. This view is supported by a parallelism of another kind:
namely, that the crossing of forms, only slightly different, is favourable
to the vigour and fertility of the offspring; and that slight changes in
the conditions of life are apparently favourable to the vigour and
fertility of all organic beings. It is not surprising that the degree of
difficulty in uniting two species, and the degree of sterility of their
hybrid offspring, should generally correspond, though due to distinct
causes; for both depend on the amount of difference of some kind between
the species which are crossed. Nor is it surprising that the facility of
effecting a first cross, the fertility of hybrids produced from it, and the
capacity of being grafted together--though this latter capacity evidently
depends on widely different circumstances--should all run to a certain
extent parallel with the systematic affinity of the forms which are
subjected to experiment; for systematic affinity attempts to express all
kinds of resemblance between all species.
"First crosses between forms known to be varieties, or sufficiently alike
to be considered as varieties, and their mongrel offspring, are very
generally, but not quite universally, fertile. Nor is this nearly general
and perfect fertility surprising, when we remember how liable we are to
argue in a circle with respect to varieties in a state of Nature; and when
we remember that the greater number of varieties have been produced under
domestication by the selection of mere external differences, and not of
differences in the reproductive system. In all other respects, excluding
fertility, there is a close general resemblance between hybrids and
mongrels."--Pp. 276-8.
We fully agree with the general tenor of this weighty passage; but forcible
as are these arguments, and little as the value of fertility or infertility
as a test of species may be, it must not be forgotten that the really
important fact, so far as the inquiry into the origin of species goes, is,
that there are such things in Nature as groups of animals and of plants,
the members of which are incapable of fertile union with those of other
groups; and that there are such things as hybrids, which are absolutely
sterile when crossed with other hybrids. For, if such phænomena as these
were exhibited by only two of those assemblages of living objects, to which
the name of species (whether it be used in its physiological or in its
morphological sense) is given, it would have to be accounted for by any
theory of the origin of species, and every theory which could not account
for it would be, so far, imperfect.
Up to this point, we have been dealing with matters of fact, and the
statements which we have laid before the reader would, to the best of our
knowledge, be admitted to contain a fair exposition of what is at present
known respecting the essential properties of species, by all who have
studied the question. And whatever may be his theoretical views, no
naturalist will probably be disposed to demur to the following summary of
that exposition:--
Living beings, whether animals or plants, are divisible into multitudes of
distinctly definable kinds, which are morphological species. They are also
divisible into groups of individuals, which breed freely together, tending
to reproduce their like, and are physiological species. Normally resembling
their parents, the offspring of members of these species are still liable
to vary; and the variation may be perpetuated by selection, as a race,
which race, in many cases, presents all the characteristics of a
morphological species. But it is not as yet proved that a race ever
exhibits, when crossed with another race of the same species, those
phænomena of hybridisation which are exhibited by many species when crossed
with other species. On the other hand, not only is it not proved that all
species give rise to hybrids infertile _inter se_, but there is much
reason to believe that, in crossing, species exhibit every gradation from
perfect sterility to perfect fertility.
Such are the most essential characteristics of species. Even were man not
one of them--a member of the same system and subject to the same laws--the
question of their origin, their causal connexion, that is, with the other
phænomena of the universe, must have attracted his attention, as soon as
his intelligence had raised itself above the level of his daily wants.
Indeed history relates that such was the case, and has embalmed for us the
speculations upon the origin of living beings, which were among the
earliest products of the dawning intellectual activity of man. In those
early days positive knowledge was not to be had, but the craving after it
needed, at all hazards, to be satisfied, and according to the country, or
the turn of thought, of the speculator, the suggestion that all living
things arose from the mud of the Nile, from a primeval egg, or from some
more anthropomorphic agency, afforded a sufficient resting-place for his
curiosity. The myths of Paganism are as dead as Osiris or Zeus, and the man
who should revive them, in opposition to the knowledge of our time, would
be justly laughed to scorn; but the coeval imaginations current among the
rude inhabitants of Palestine, recorded by writers whose very name and age
are admitted by every scholar to be unknown, have unfortunately not yet
shared their fate, but, even at this day, are regarded by nine-tenths of
the civilised world as the authoritative standard of fact and the criterion
of the justice of scientific conclusions, in all that relates to the origin
of things, and, among them, of species. In this nineteenth century, as at
the dawn of modern physical science, the cosmogony of the semi-barbarous
Hebrew is the incubus of the philosopher and the opprobrium of the
orthodox. Who shall number the patient and earnest seekers after truth,
from the days of Galileo until now, whose lives have been embittered and
their good name blasted by the mistaken zeal of Bibliolaters? Who shall
count the host of weaker men whose sense of truth has been destroyed in the
effort to harmonise impossibilities--whose life has been wasted in the
attempt to force the generous new wine of Science into the old bottles of
Judaism, compelled by the outcry of the same strong party?
It is true that if philosophers have suffered, their cause has been amply
avenged. Extinguished theologians lie about the cradle of every science as
the strangled snakes beside that of Hercules; and history records that
whenever science and orthodoxy have been fairly opposed, the latter has
been forced to retire from the lists, bleeding and crushed if not
annihilated; scotched, if not slain. But orthodoxy is the Bourbon of the
world of thought. It learns not, neither can it forget; and though, at
present, bewildered and afraid to move, it is as willing as ever to insist
that the first chapter of Genesis contains the beginning and the end of
sound science; and to visit, with such petty thunderbolts as its
half-paralysed hands can hurl, those who refuse to degrade Nature to the
level of primitive Judaism.
Philosophers, on the other hand, have no such aggressive tendencies. With
eyes fixed on the noble goal to which "per aspera et ardua" they tend, they
may, now and then, be stirred to momentary wrath by the unnecessary
obstacles with which the ignorant, or the malicious, encumber, if they
cannot bar, the difficult path; but why should their souls be deeply vexed?
The majesty of Fact is on their side, and the elemental forces of Nature
are working for them. Not a star comes to the meridian at its calculated
time but testifies to the justice of their methods--their beliefs are "one
with the falling rain and with the growing corn." By doubt they are
established, and open inquiry is their bosom friend. Such men have no fear
of traditions however venerable, and no respect for them when they become
mischievous and obstructive; but they have better than mere antiquarian
business in hand, and if dogmas, which ought to be fossil but are not, are
not forced upon their notice, they are too happy to treat them as
non-existent.
* * * * *
The hypotheses respecting the origin of species which profess to stand upon
a scientific basis, and, as such, alone demand serious attention, are of
two kinds. The one, the "special creation" hypothesis, presumes every
species to have originated from one or more stocks, these not being the
result of the modification of any other form of living matter--or arising
by natural agencies--but being produced, as such, by a supernatural
creative act.
The other, the so-called "transmutation" hypothesis, considers that all
existing species are the result of the modification of pre-existing
species, and those of their predecessors, by agencies similar to those
which at the present day produce varieties and races, and therefore in an
altogether natural way; and it is a probable, though not a necessary
consequence of this hypothesis, that all living beings have arisen from a
single stock. With respect to the origin of this primitive stock, or
stocks, the doctrine of the origin of species is obviously not necessarily
concerned. The transmutation hypothesis, for example, is perfectly
consistent either with the conception of a special creation of the
primitive germ, or with the supposition of its having arisen, as a
modification of inorganic matter, by natural causes.
The doctrine of special creation owes its existence very largely to the
supposed necessity of making science accord with the Hebrew cosmogony; but
it is curious to observe that, as the doctrine is at present maintained by
men of science, it is as hopelessly inconsistent with the Hebrew view as
any other hypothesis.
If there be any result which has come more clearly out of geological
investigation than another, it is, that the vast series of extinct animals
and plants is not divisible, as it was once supposed to be, into distinct
groups, separated by sharply-marked boundaries. There are no great gulfs
between epochs and formations--no successive periods marked by the
appearance of plants, of water animals, and of land animals, _en
masse_. Every year adds to the list of links between what the older
geologists supposed to be widely separated epochs: witness the crags
linking the drift with older tertiaries; the Maestricht beds linking the
tertiaries with the chalk; the St. Cassian beds exhibiting an abundant
fauna of mixed mesozoic and palaeozoic types, in rocks of an epoch once
supposed to be eminently poor in life; witness, lastly, the incessant
disputes as to whether a given stratum shall be reckoned devonian or
carboniferous, silurian or devonian, cambrian or silurian.
This truth is further illustrated in a most interesting manner by the
impartial and highly competent testimony of M. Pictet, from whose
calculations of what percentage of the genera of animals, existing in any
formation, lived during the preceding formation, it results that in no case
is the proportion less than _one-third_, or 33 per cent. It is the
triassic formation, or the commencement of the mesozoic epoch, which has
received the smallest inheritance from preceding ages. The other formations
not uncommonly exhibit 60, 80, or even 94 per cent, of genera in common
with those whose remains are imbedded in their predecessor. Not only is
this true, but the subdivisions of each formation exhibit new species
characteristic of, and found only in, them; and, in many cases, as in the
lias for example, the separate beds of these subdivisions are distinguished
by well-marked and peculiar forms of life. A section, a hundred feet thick,
will exhibit, at different heights, a dozen species of ammonite, none of
which passes beyond its particular zone of limestone, or clay, into the
zone below it or into that above it; so that those who adopt the doctrine
of special creation must be prepared to admit, that at intervals of time,
corresponding with the thickness of these beds, the Creator thought fit to
interfere with the natural course of events for the purpose of making a new
ammonite. It is not easy to transplant oneself into the frame of mind of
those who can accept such a conclusion as this, on any evidence short of
absolute demonstration; and it is difficult to see what is to be gained by
so doing, since, as we have said, it is obvious that such a view of the
origin of living beings is utterly opposed to the Hebrew cosmogony.
Deserving no aid from the powerful arm of Bibliolatry, then, does the
received form of the hypothesis of special creation derive any support from
science or sound logic? Assuredly not much. The arguments brought forward
in its favour all take one form: If species were not supernaturally
created, we cannot understand the facts _x_, or _y_, or _z_;
we cannot understand the structure of animals or plants, unless we suppose
they were contrived for special ends; we cannot understand the structure of
the eye, except by supposing it to have been made to see with; we cannot
understand instincts, unless we suppose animals to have been miraculously
endowed with them.
As a question of dialectics, it must be admitted that this sort of
reasoning is not very formidable to those who are not to be frightened by
consequences. It is an _argumentum ad ignorantiam_--take this
explanation or be ignorant. But suppose we prefer to admit our ignorance
rather than adopt a hypothesis at variance with all the teachings of
Nature? Or, suppose for a moment we admit the explanation, and then
seriously ask ourselves how much the wiser are we; what does the
explanation explain? Is it any more than a grandiloquent way of announcing
the fact, that we really know nothing about the matter? A phenomenon is
explained when it is shown to be a case of some general law of Nature; but
the supernatural interposition of the Creator can, by the nature of the
case, exemplify no law, and if species have really arisen in this way, it
is absurd to attempt to discuss their origin.
Or, lastly, let us ask ourselves whether any amount of evidence which the
nature of our faculties permits us to attain, can justify us in asserting
that any phenomenon is out of the reach of natural causation. To this end
it is obviously necessary that we should know all the consequences to which
all possible combinations, continued through unlimited time, can give rise.
If we knew these, and found none competent to originate species, we should
have good ground for denying their origin by natural causation. Till we
know them, any hypothesis is better than one which involves us in such
miserable presumption.
But the hypothesis of special creation is not only a mere specious mask for
our ignorance; its existence in Biology marks the youth and imperfection of
the science. For what is the history of every science but the history of
the elimination of the notion of creative, or other interferences, with the
natural order of the phænomena which are the subject-matter of that
science? When Astronomy was young "the morning stars sang together for
joy," and the planets were guided in their courses by celestial hands. Now,
the harmony of the stars has resolved itself into gravitation according to
the inverse squares of the distances, and the orbits of the planets are
deducible from the laws of the forces which allow a schoolboy's stone to
break a window. The lightning was the angel of the Lord; but it has pleased
Providence, in these modern times, that science should make it the humble
messenger of man, and we know that every flash that shimmers about the
horizon on a summer's evening is determined by ascertainable conditions,
and that its direction and brightness might, if our knowledge of these were
great enough, have been calculated.
The solvency of great mercantile companies rests on the validity of the
laws which have been ascertained to govern the seeming irregularity of that
human life which the moralist bewails as the most uncertain of things;
plague, pestilence, and famine are admitted, by all but fools, to be the
natural result of causes for the most part fully within human control, and
not the unavoidable tortures inflicted by wrathful Omnipotence upon His
helpless handiwork.
Harmonious order governing eternally continuous progress--the web and woof
of matter and force interweaving by slow degrees, without a broken thread,
that veil which lies between us and the Infinite--that universe which alone
we know or can know; such is the picture which science draws of the world,
and in proportion as any part of that picture is in unison with the rest,
so may we feel sure that it is rightly painted. Shall Biology alone remain
out of harmony with her sister sciences?
Such arguments against the hypothesis of the direct creation of species as
these are plainly enough deducible from general considerations; but there
are, in addition, phenomena exhibited by species themselves, and yet not so
much a part of their very essence as to have required earlier mention,
which are in the highest degree perplexing, if we adopt the popularly
accepted hypothesis. Such are the facts of distribution in space and in
time; the singular phenomena brought to light by the study of development;
the structural relations of species upon which our systems of
classification are founded; the great doctrines of philosophical anatomy,
such as that of homology, or of the community of structural plan exhibited
by large groups of species differing very widely in their habits and
functions.
The species of animals which inhabit the sea on opposite sides of the
isthmus of Panama are wholly distinct;[Footnote: Recent investigations tend
to show that this statement is not strictly accurate.--1870.] the animals
and plants which inhabit islands are commonly distinct from those of the
neighbouring mainlands, and yet have a similarity of aspect. The mammals of
the latest tertiary epoch in the Old and New Worlds belong to the same
genera, or family groups, as those which now inhabit the same great
geographical area. The crocodilian reptiles which existed in the earliest
secondary epoch were similar in general structure to those now living, but
exhibit slight differences in their vertebræ, nasal passages, and one or
two other points. The guinea-pig has teeth which are shed before it is
born, and hence can never subserve the masticatory purpose for which they
seem contrived, and, in like manner, the female dugong has tusks which
never cut the gum. All the members of the same great group run through
similar conditions in their development, and all their parts, in the adult
state, are arranged according to the same plan. Man is more like a gorilla
than a gorilla is like a lemur. Such are a few, taken at random, among the
multitudes of similar facts which modern research has established; but when
the student seeks for an explanation of them from the supporters of the
received hypothesis of the origin of species, the reply he receives is, in
substance, of Oriental simplicity and brevity--"Mashallah! it so pleases
God!" There are different species on opposite sides of the isthmus of
Panama, because they were created different on the two sides. The pliocene
mammals are like the existing ones, because such was the plan of creation;
and we find rudimental organs and similarity of plan, because it has
pleased the Creator to set before Himself a "divine exemplar or archetype,"
and to copy it in His works; and somewhat ill, those who hold this view
imply, in some of them. That such verbal hocus-pocus should be received as
science will one day be regarded as evidence of the low state of
intelligence in the nineteenth century, just as we amuse ourselves with the
phraseology about Nature's abhorrence of a vacuum, wherewith Torricellis
compatriots were satisfied to explain the rise of water in a pump. And be
it recollected that this sort of satisfaction works not only negative but
positive ill, by discouraging inquiry, and so depriving man of the usufruct
of one of the most fertile fields of his great patrimony, Nature.
The objections to the doctrine of the origin of species by special creation
which have been detailed, must have occurred, with more or less force, to
the mind of every one who has seriously and independently considered the
subject. It is therefore no wonder that, from time to time, this hypothesis
should have been met by counter hypotheses, all as well, and some better
founded than itself; and it is curious to remark that the inventors of the
opposing views seem to have been led into them as much by their knowledge
of geology, as by their acquaintance with biology. In fact, when the mind
has once admitted the conception of the gradual production of the present
physical state of our globe, by natural causes operating through long ages
of time, it will be little disposed to allow that living beings have made
their appearance in another way, and the speculations of De Maillet and his
successors are the natural complement of Scilla's demonstration of the true
nature of fossils.
A contemporary of Newton and of Leibnitz, sharing therefore in the
intellectual activity of the remarkable age which witnessed the birth of
modern physical science, Benoît de Maillet spent a long life as a consular
agent of the French Government in various Mediterranean ports. For sixteen
years, in fact, he held the office of Consul-General in Egypt, and the
wonderful phenomena offered by the valley of the Nile appear to have
strongly impressed his mind, to have directed his attention to all facts of
a similar order which came within his observation, and to have led him to
speculate on the origin of the present condition of our globe and of its
inhabitants. But, with all his ardour for science, De Maillet seems to have
hesitated to publish views which, notwithstanding the ingenious attempts to
reconcile them with the Hebrew hypothesis contained in the preface to
"Telliamed," were hardly likely to be received with favour by his
contemporaries.
But a short time had elapsed since more than one of the great anatomists
and physicists of the Italian school had paid dearly for their endeavours
to dissipate some of the prevalent errors; and their illustrious pupil,
Harvey, the founder of modern physiology, had not fared so well, in a
country less oppressed by the benumbing influences of theology, as to tempt
any man to follow his example. Probably not uninfluenced by these
considerations, his Catholic majesty's Consul-General for Egypt kept his
theories to himself throughout a long life, for "Telliamed," the only
scientific work which is known to have proceeded from his pen, was not
printed till 1735, when its author had reached the ripe age of
seventy-nine; and though De Maillet lived three years longer, his book was
not given to the world before 1748. Even then it was anonymous to those who
were not in the secret of the anagrammatic character of its title; and the
preface and dedication are so worded as, in case of necessity, to give the
printer a fair chance of falling back on the excuse that the work was
intended for a mere _jeu d'esprit_.
The speculations of the suppositious Indian sage, though quite as sound as
those of many a "Mosaic Geology," which sells exceedingly well, have no
great value if we consider them by the light of modern science. The waters
are supposed to have originally covered the whole globe; to have deposited
the rocky masses which compose its mountains by processes comparable to
those which are now forming mud, sand, and shingle; and then to have
gradually lowered their level, leaving the spoils of their animal and
vegetable inhabitants embedded in the strata. As the dry land appeared,
certain of the aquatic animals are supposed to have taken to it, and to
have become gradually adapted to terrestrial and aërial modes of existence.
But if we regard the general tenor and style of the reasoning in relation
to the state of knowledge of the day, two circumstances appear very well
worthy of remark. The first, that De Maillet had a notion of the
modifiability of living forms (though without any precise information on
the subject), and how such modifiability might account for the origin of
species; the second, that he very clearly apprehended the great modern
geological doctrine, so strongly insisted upon by Hutton, and so ably and
comprehensively expounded by Lyell, that we must look to existing causes
for the explanation of past geological events. Indeed, the following
passage of the preface, in which De Maillet is supposed to speak of the
Indian philosopher Telliamed, his _alter ego,_ might have been written
by the most philosophical uniformitarian of the present day:--
"Ce qu'il y a d'étonnant, est que pour arriver à ces connaissances il
semble avoir perverti l'ordre naturel, puisqu'au lieu de s'attacher d'abord
à rechercher l'origine de notre globe il a commence par travailler à
s'instruire de la nature. Mais à l'entendre, ce renversement de l'ordre a
été pour lui l'effet d'un génie favorable qui l'a conduit pas à pas et
comme par la main aux découvertes les plus sublimes. C'est en décomposant
la substance de ce globe par tine anatomie exacte de toutes ses parties
qu'il a premierement appris de quelles matières il était composé et quels
arrangemens ces mêmes matières observaient entre elles. Ces lumieres
jointes à l'esprit de comparaison toujours nécessaire à quiconque
entreprend de percer les voiles dont la nature aime à se cacher, ont servi
de guide à notre philosophe pour parvenir à des connoissances plus
intéressantes. Par la matière et l'arrangement de ces compositions il
prétend avoir reconnu quelle est la véritable origine de ce globe que nous
habitons, comment et par qui il a été formé."-Pp. xix. xx.
But De Maillet was before his age, and as could hardly fail to happen to
one who speculated on a zoological and botanical question before Linnæus,
and on a physiological problem before Haller, he fell into great errors
here and there; and hence, perhaps, the general neglect of his work.
Robinet's speculations are rather behind, than in advance of, those of De
Maillet; and though Linnæus may have played with the hypothesis of
transmutation, it obtained no serious support until Lamarck adopted it, and
advocated it with great ability in his "Philosophie Zoologique."
Impelled towards the hypothesis of the transmutation of species, partly by
his general cosmological and geological views; partly by the conception of
a graduated, though irregularly branching, scale of being, which had arisen
out of his profound study of plants and of the lower forms of animal life,
Lamarck, whose general line of thought often closely resembles that of De
Maillet, made a great advance upon the crude and merely speculative manner
in which that writer deals with the question of the origin of living
beings, by endeavouring to find physical causes competent to effect that
change of one species into another, which De Maillet had only supposed to
occur. And Lamarck conceived that he had found in Nature such causes, amply
sufficient for the purpose in view. It is a physiological fact, he says,
that organs are increased in size by action, atrophied by inaction; it is
another physiological fact that modifications produced are transmissible to
offspring. Change the actions of an animal, therefore, and you will change
its structure, by increasing the development of the parts newly brought
into use and by the diminution of those less used; but by altering the
circumstances which surround it you will alter its actions, and hence, in
the long run, change of circumstance must produce change of organisation.
All the species of animals, therefore, are, in Lamarck's view, the result
of the indirect action of changes of circumstance, upon those primitive
germs which he considered to have originally arisen, by spontaneous
generation, within the waters of the globe. It is curious, however, that
Lamarck should insist so strongly [Footnote: See _Phil. Zoologique_,
vol. i. p. 222. et seq.] as he has done, that circumstances never in any
degree directly modify the form or the organisation of animals, but only
operate by changing their wants and consequently their actions; for he
thereby brings upon himself the obvious question, How, then, do plants,
which cannot be said to have wants or actions, become modified? To this he
replies, that they are modified by the changes in their nutritive
processes, which are effected by changing circumstances; and it does not
seem to have occurred to him that such changes might be as well supposed to
take place among animals.
When we have said that Lamarck felt that mere speculation was not the way
to arrive at the origin of species, but that it was necessary, in order to
the establishment of any sound theory on the subject, to discover by
observation or otherwise, some _vera causa_, competent to give rise to
them; that he affirmed the true order of classification to coincide with
the order of their development one from another; that he insisted on the
necessity of allowing sufficient time, very strongly; and that all the
varieties of instinct and reason were traced back by him to the same cause
as that which has given rise to species, we have enumerated his chief
contributions to the advance of the question. On the other hand, from his
ignorance of any power in Nature competent to modify the structure of
animals, except the development of parts, or atrophy of them, in
consequence of a change of needs, Lamarck was led to attach infinitely
greater weight than it deserves to this agency, and the absurdities into
which he was led have met with deserved condemnation. Of the struggle for
existence, on which, as we shall see, Mr. Darwin lays such great stress, he
had no conception; indeed, he doubts whether there really are such things
as extinct species, unless they be such large animals as may have met their
death at the hands of man; and so little does he dream of there being any
other destructive causes at work, that, in discussing the possible
existence of fossil shells, he asks, "Pourquoi d'ailleurs seroient-ils
perdues dès que l'homme n'a pu opérer leur destruction?" ("Phil. Zool.,"
vol. i. p. 77.) Of the influence of selection Lamarck has as little notion,
and he makes no use of the wonderful phenomena which are exhibited by
domesticated animals, and illustrate its powers. The vast influence of
Cuvier was employed against the Lamarckian views, and, as the untenability
of some of his conclusions was easily shown, his doctrines sank under the
opprobrium of scientific, as well as of theological, heterodoxy. Nor have
the efforts made of late years to revive them tended to re-establish their
credit in the minds of sound thinkers acquainted with the facts of the
case; indeed it may be doubted whether Lamarck has not suffered more from
his friends than from his foes.
Two years ago, in fact, though we venture to question if even the strongest
supporters of the special creation hypothesis had not, now and then, an
uneasy consciousness that all was not right, their position seemed more
impregnable than ever, if not by its own inherent strength, at any rate by
the obvious failure of all the attempts which had been made to carry it. On
the other hand, however much the few, who thought deeply on the question of
species, might be repelled by the generally received dogmas, they saw no
way of escaping from them save by the adoption of suppositions so little
justified by experiment or by observation as to be at least equally
distasteful.
The choice lay between two absurdities and a middle condition of uneasy
scepticism; which last, however unpleasant and unsatisfactory, was
obviously the only justifiable state of mind under the circumstances.
Such being the general ferment in the minds of naturalists, it is no wonder
that they mustered strong in the rooms of the Linnæan Society, on the 1st
of July of the year 1858, to hear two papers by authors living on opposite
sides of the globe, working out their results independently, and yet
professing to have discovered one and the same solution of all the problems
connected with species. The one of these authors was an able naturalist,
Mr. Wallace, who had been employed for some years in studying the
productions of the islands of the Indian Archipelago, and who had forwarded
a memoir embodying his views to Mr. Darwin, for communication to the
Linnæan Society. On perusing the essay, Mr. Darwin was not a little
surprised to find that it embodied some of the leading ideas of a great
work which he had been preparing for twenty years, and parts of which,
containing a development of the very same views, had been perused by his
private friends fifteen or sixteen years before. Perplexed in what manner
to do full justice both to his friend and to himself, Mr. Darwin placed the
matter in the hands of Dr. Hooker and Sir Charles Lyell, by whose advice he
communicated a brief abstract of his own views to the Linnæan Society, at
the same time that Mr. Wallace's paper was read. Of that abstract, the work
on the "Origin of Species" is an enlargement; but a complete statement of
Mr. Darwin's doctrine is looked for in the large and well-illustrated work
which he is said to be preparing for publication.
The Darwinian hypothesis has the merit of being eminently simple and
comprehensible in principle, and its essential positions may be stated in a
very few words: all species have been produced by the development of
varieties from common stocks; by the conversion of these, first into
permanent races and then into new species, by the process of _natural
selection_, which process is essentially identical with that artificial
selection by which man has originated the races of domestic animals--the
_struggle for existence_ taking the place of man, and exerting, in the
case of natural selection, that selective action which he performs in
artificial selection.
The evidence brought forward by Mr. Darwin in support of his hypothesis is
of three kinds. First, he endeavours to prove that species may be
originated by selection; secondly, he attempts to show that natural causes
are competent to exert selection; and thirdly, he tries to prove that the
most remarkable and apparently anomalous phænomena exhibited by the
distribution, development, and mutual relations of species, can be shown to
be deducible from the general doctrine of their origin, which he propounds,
combined with the known facts of geological change; and that, even if all
these phænomena are not at present explicable by it, none are necessarily
inconsistent with it.
There cannot be a doubt that the method of inquiry which Mr. Darwin has
adopted is not only rigorously in accordance with the canons of scientific
logic, but that it is the only adequate method. Critics exclusively trained
in classics or in mathematics, who have never determined a scientific fact
in their lives by induction from experiment or observation, prate learnedly
about Mr. Darwin's method, which is not inductive enough, not Baconian
enough, forsooth, for them. But even if practical acquaintance with the
process of scientific investigation is denied them, they may learn, by the
perusal of Mr. Mill's admirable chapter "On the Deductive Method," that
there are multitudes of scientific inquiries in which the method of pure
induction helps the investigator but a very little way.
"The mode of investigation," says Mr. Mill, "which, from the proved
inapplicability of direct methods of observation and experiment, remains to
us as the main source of the knowledge we possess, or can acquire,
respecting the conditions and laws of recurrence of the more complex
phænomena, is called, in its most general expression, the deductive method,
and consists of three operations: the first, one of direct induction; the
second, of ratiocination; and the third, of verification."
Now, the conditions which have determined the existence of species are not
only exceedingly complex, but, so far as the great majority of them are
concerned, are necessarily beyond our cognisance. But what Mr. Darwin has
attempted to do is in exact accordance with the rule laid down by Mr. Mill;
he has endeavoured to determine certain great facts inductively, by
observation and experiment; he has then reasoned from the data thus
furnished; and lastly, he has tested the validity of his ratiocination by
comparing his deductions with the observed facts of Nature. Inductively,
Mr. Darwin endeavours to prove that species arise in a given way.
Deductively, he desires to show that, if they arise in that way, the facts
of distribution, development, classification, &c., may be accounted for,
_i.e._ may be deduced from their mode of origin, combined with
admitted changes in physical geography and climate, during an indefinite
period. And this explanation, or coincidence of observed with deduced
facts, is, so far as it extends, a verification of the Darwinian view.
There is no fault to be found with Mr. Darwin's method, then; but it is
another question whether he has fulfilled all the conditions imposed by
that method. Is it satisfactorily proved, in fact, that species may be
originated by selection? that there is such a thing as natural selection?
that none of the phænomena exhibited by species are inconsistent with the
origin of species in this way? If these questions can be answered in the
affirmative, Mr. Darwin's view steps out of the rank of hypotheses into
those of proved theories; but, so long as the evidence at present adduced
falls short of enforcing that affirmation, so long, to our minds, must the
new doctrine be content to remain among the former--an extremely valuable,
and in the highest degree probable, doctrine, indeed the only extant
hypothesis which is worth anything in a scientific point of view; but still
a hypothesis, and not yet the theory of species.
After much consideration, and with assuredly no bias against Mr. Darwin's
views, it is our clear conviction that, as the evidence stands, it is not
absolutely proven that a group of animals, having all the characters
exhibited by species in Nature, has ever been originated by selection,
whether artificial or natural. Groups having the morphological character of
species--distinct and permanent races in fact--have been so produced over
and over again; but there is no positive evidence, at present, that any
group of animals has, by variation and selective breeding, given rise to
another group which was, even in the least degree, infertile with the
first. Mr. Darwin is perfectly aware of this weak point, and brings forward
a multitude of ingenious and important arguments to diminish the force of
the objection. We admit the value of these arguments to their fullest
extent; nay, we will go so far as to express our belief that experiments,
conducted by a skilful physiologist, would very probably obtain the desired
production of mutually more or less infertile breeds from a common stock,
in a comparatively few years; but still, as the case stands at present,
this "little rift within the lute" is not to be disguised nor overlooked.
In the remainder of Mr. Darwin's argument our own private ingenuity has not
hitherto enabled us to pick holes of any great importance; and judging by
what we hear and read, other adventurers in the same field do not seem to
have been much more fortunate. It has been urged, for instance, that in his
chapters on the struggle for existence and on natural selection, Mr. Darwin
does not so much prove that natural selection does occur, as that it must
occur; but, in fact, no other sort of demonstration is attainable. A race
does not attract our attention in Nature until it has, in all probability,
existed for a considerable time, and then it is too late to inquire into
the conditions of its origin. Again, it is said that there is no real
analogy between the selection which takes place under domestication, by
human influence, and any operation which can be effected by Nature, for man
interferes intelligently. Reduced to its elements, this argument implies
that an effect produced with trouble by an intelligent agent must, _à
fortiori,_ be more troublesome, if not impossible, to an unintelligent
agent. Even putting aside the question whether Nature, acting as she does
according to definite and invariable laws, can be rightly called an
unintelligent agent, such a position as this is wholly untenable. Mix salt
and sand, and it shall puzzle the wisest of men, with his mere natural
appliances, to separate all the grains of sand from all the grains of salt;
but a shower of rain will effect the same object in ten minutes. And so,
while man may find it tax all his intelligence to separate any variety
which arises, and to breed selectively from it, the destructive agencies
incessantly at work in Nature, if they find one variety to be more soluble
in circumstances than the other, will inevitably, in the long run,
eliminate it.
A frequent and a just objection to the Lamarckian hypothesis of the
transmutation of species is based upon the absence of transitional forms
between many species. But against the Darwinian hypothesis this argument
has no force. Indeed, one of the most valuable and suggestive parts of Mr.
Darwin's work is that in which he proves, that the frequent absence of
transitions is a necessary consequence of his doctrine, and that the stock
whence two or more species have sprung, need in no respect be intermediate
between these species. If any two species have arisen from a common stock
in the same way as the carrier and the pouter, say, have arisen from the
rock-pigeon, then the common stock of these two species need be no more
intermediate between the two than the rock-pigeon is between the carrier
and pouter. Clearly appreciate the force of this analogy, and all the
arguments against the origin of species by selection, based on the absence
of transitional forms, fall to the ground. And Mr. Darwin's position might,
we think, have been even stronger than it is if he had not embarrassed
himself with the aphorism, "_Natura non facit saltum_," which turns up
so often in his pages. We believe, as we have said above, that Nature does
make jumps now and then, and a recognition of the fact is of no small
importance in disposing of many minor objections to the doctrine of
transmutation.
But we must pause. The discussion of Mr. Darwin's arguments in detail would
lead us far beyond the limits within which we proposed, at starting, to
confine this article. Our object has been attained if we have given an
intelligible, however brief, account of the established facts connected
with species, and of the relation of the explanation of those facts offered
by Mr. Darwin to the theoretical views held by his predecessors and his
contemporaries, and, above all, to the requirements of scientific logic. We
have ventured to point out that it does not, as yet, satisfy all those
requirements; but we do not hesitate to assert that it is as superior to
any preceding or contemporary hypothesis, in the extent of observational
and experimental basis on which it rests, in its rigorously scientific
method, and in its power of explaining biological phenomena, as was the
hypothesis of Copernicus to the speculations of Ptolemy. But the planetary
orbits turned out to be not quite circular after all, and, grand as was the
service Copernicus rendered to science, Kepler and Newton had to come after
him. What if the orbit of Darwinism should be a little too circular? What
if species should offer residual phænomena, here and there, not explicable
by natural selection? Twenty years hence naturalists may be in a position
to say whether this is, or is not, the case; but in either event they will
owe the author of "The Origin of Species" an immense debt of gratitude. We
should leave a very wrong impression on the reader's mind if we permitted
him to suppose that the value of that work depends wholly on the ultimate
justification of the theoretical views which it contains. On the contrary,
if they were disproved to-morrow, the book would still be the best of its
kind--the most compendious statement of well-sifted facts bearing on the
doctrine of species that has ever appeared. The chapters on Variation, on
the Struggle for Existence, on Instinct, on Hybridism, on the Imperfection
of the Geological Record, on Geographical Distribution, have not only no
equals, but, so far as our knowledge goes, no competitors, within the range
of biological literature. And viewed as a whole, we do not believe that,
since the publication of Von Baer's "Researches on Development," thirty
years ago, any work has appeared calculated to exert so large an influence,
not only on the future of Biology, but in extending the domination of
Science over regions of thought into which she has, as yet, hardly
penetrated.
III
CRITICISMS ON "THE ORIGIN OF SPECIES"
[1864]
1. UEBER DIE DARWIN'SCHE SCHÖPFUNGSTHEORIE; EIN VORTRAG, Von A. KÖLLIKER.
Leipzig, 1864.
2. EXAMINATION DU LIVRE DE M. DARWIN SUR L'ORIGINE DES ESPÈCES. Par P.
FLOURENS. Paris, 1864.
In the course of the present year several foreign commentaries upon Mr.
Darwin's great work have made their appearance. Those who have perused that
remarkable chapter of the "Antiquity of Man," in which Sir Charles Lyell
draws a parallel between the development of species and that of languages,
will be glad to hear that one of the most eminent philologers of Germany,
Professor Schleicher, has, independently, published a most instructive and
philosophical pamphlet (an excellent notice of which is to be found in the
_Reader_, for February 27th of this year) supporting similar views
with all the weight of his special knowledge and established authority as a
linguist. Professor Haeckel, to whom Schleicher addresses himself,
previously took occasion, in his splendid monograph on the
_Radiolaria_,[Footnote: _Die Radiolarien: eine Monographie_, p.
231.] to express his high appreciation of, and general concordance with,
Mr. Darwin's views.
But the most elaborate criticisms of the "Origin of Species" which have
appeared are two works of very widely different merit, the one by Professor
Kölliker, the well-known anatomist and histologist of Würzburg; the other
by M. Flourens, Perpetual Secretary of the French Academy of Sciences.
Professor Kölliker's critical essay "Upon the Darwinian Theory" is, like
all that proceeds from the pen of that thoughtful and accomplished writer,
worthy of the most careful consideration. It comprises a brief but clear
sketch of Darwin's views, followed by an enumeration of the leading
difficulties in the way of their acceptance; difficulties which would
appear to be insurmountable to Professor Kölliker, inasmuch as he proposes
to replace Mr. Darwin's Theory by one which he terms the "Theory of
Heterogeneous Generation." We shall proceed to consider first the
destructive, and secondly, the constructive portion of the essay.
We regret to find ourselves compelled to dissent very widely from many of
Professor Kölliker's remarks; and from none more thoroughly than from those
in which he seeks to define what we may term the philosophical position of
Darwinism.
"Darwin," says Professor Kölliker, "is, in the fullest sense of the word, a
Teleologist. He says quite distinctly (First Edition, pp. 199, 200) that
every particular in the structure of an animal has been created for its
benefit, and he regards the whole series of animal forms only from this
point of view."
And again:
"7. The teleological general conception adopted by Darwin is a mistaken
one.
"Varieties arise irrespectively of the notion of purpose, or of utility,
according to general laws of Nature, and may be either useful, or hurtful,
or indifferent.
"The assumption that an organism exists only on account of some definite
end in view, and represents something more than the incorporation of a
general idea, or law, implies a one-sided conception of the universe.
Assuredly, every organ has, and every organism fulfils, its end, but its
purpose is not the condition of its existence. Every organism is also
sufficiently perfect for the purpose it serves, and in that, at least, it
is useless to seek for a cause of its improvement."
It is singular how differently one and the same book will impress different
minds. That which struck the present writer most forcibly on his first
perusal of the "Origin of Species" was the conviction that Teleology, as
commonly understood, had received its deathblow at Mr. Darwin's hands. For
the teleological argument runs thus: an organ or organism (A) is precisely
fitted to perform a function or purpose (B); therefore it was specially
constructed to perform that function. In Paley's famous illustration, the
adaptation of all the parts of the watch to the function, or purpose, of
showing the time, is held to be evidence that the watch was specially
contrived to that end; on the ground, that the only cause we know of,
competent to produce such an effect as a watch which shall keep time, is a
contriving intelligence adapting the means directly to that end.
Suppose, however, that any one had been able to show that the watch had not
been made directly by any person, but that it was the result of the
modification of another watch which kept time but poorly; and that this
again had proceeded from a structure which could hardly be called a watch
at all--seeing that it had no figures on the dial and the hands were
rudimentary; and that going back and back in time we came at last to a
revolving barrel as the earliest traceable rudiment of the whole fabric.
And imagine that it had been possible to show that all these changes had
resulted, first, from a tendency of the structure to vary indefinitely; and
secondly, from something in the surrounding world which helped all
variations in the direction of an accurate time-keeper, and checked all
those in other directions; then it is obvious that the force of Paley's
argument would be gone. For it would be demonstrated that an apparatus
thoroughly well adapted to a particular purpose might be the result of a
method of trial and error worked by unintelligent agents, as well as of the
direct application of the means appropriate to that end, by an intelligent
agent.
Now it appears to us that what we have here, for illustration's sake,
supposed to be done with the watch, is exactly what the establishment of
Darwin's Theory will do for the organic world. For the notion that every
organism has been created as it is and launched straight at a purpose, Mr.
Darwin substitutes the conception of something which may fairly be termed a
method of trial and error. Organisms vary incessantly; of these variations
the few meet with surrounding conditions which suit them and thrive; the
many are unsuited and become extinguished.
According to Teleology, each organism is like a rifle bullet fired straight
at a mark; according to Darwin, organisms are like grapeshot of which one
hits something and the rest fall wide.
For the teleologist an organism exists because it was made for the
conditions in which it is found; for the Darwinian an organism exists
because, out of many of its kind, it is the only one which has been able to
persist in the conditions in which it is found.
Teleology implies that the organs of every organism are perfect and cannot
be improved; the Darwinian theory simply affirms that they work well enough
to enable the organism to hold its own against such competitors as it has
met with, but admits the possibility of indefinite improvement. But an
example may bring into clearer light the profound opposition between the
ordinary teleological, and the Darwinian, conception.
Cats catch mice, small birds and the like, very well. Teleology tells us
that they do so because they were expressly constructed for so doing--that
they are perfect mousing apparatuses, so perfect and so delicately adjusted
that no one of their organs could be altered, without the change involving
the alteration of all the rest. Darwinism affirms on the contrary, that
there was no express construction concerned in the matter; but that among
the multitudinous variations of the Feline stock, many of which died out
from want of power to resist opposing influences, some, the cats, were
better fitted to catch mice than others, whence they throve and persisted,
in proportion to the advantage over their fellows thus offered to them.
Far from imagining that cats exist _in order_ to catch mice well,
Darwinism supposes that cats exist because they catch mice well--mousing
being not the end, but the condition, of their existence. And if the cat
type has long persisted as we know it, the interpretation of the fact upon
Darwinian principles would be, not that the cats have remained invariable,
but that such varieties as have incessantly occurred have been, on the
whole, less fitted to get on in the world than the existing stock.
If we apprehend the spirit of the "Origin of Species" rightly, then,
nothing can be more entirely and absolutely opposed to Teleology, as it is
commonly understood, than the Darwinian Theory. So far from being a
"Teleologist in the fullest sense of the word," we should deny that he is a
Teleologist in the ordinary sense at all; and we should say that, apart
from his merits as a naturalist, he has rendered a most remarkable service
to philosophical thought by enabling the student of Nature to recognise, to
their fullest extent, those adaptations to purpose which are so striking in
the organic world, and which Teleology has done good service in keeping
before our minds, without being false to the fundamental principles of a
scientific conception of the universe. The apparently diverging teachings
of the Teleologist and of the Morphologist are reconciled by the Darwinian
hypothesis.
But leaving our own impressions of the "Origin of Species," and turning to
those passages especially cited by Professor Kölliker, we cannot admit that
they bear the interpretation he puts upon them. Darwin, if we read him
rightly, does _not_ affirm that every detail in the structure of an
animal has been created for its benefit. His words are (p. 199):--
"The foregoing remarks lead me to say a few words on the protest lately
made by some naturalists against the utilitarian doctrine that every detail
of structure has been produced for the good of its possessor. They believe
that very many structures have been created for beauty in the eyes of man,
or for mere variety. This doctrine, if true, would be absolutely fatal to
my theory--yet I fully admit that many structures are of no direct use to
their possessor."
And after sundry illustrations and qualifications, he concludes (p. 200):--
"Hence every detail of structure in every living creature (making some
little allowance for the direct action of physical conditions) may be
viewed either as having been of special use to some ancestral form, or as
being now of special use to the descendants of this form--either directly,
or indirectly, through the complex laws of growth."
But it is one thing to say, Darwinically, that every detail observed in an
animal's structure is of use to it, or has been of use to its ancestors;
and quite another to affirm, teleologically, that every detail of an
animal's structure has been created for its benefit. On the former
hypothesis, for example, the teeth of the foetal _Baltæna_ have a
meaning; on the latter, none. So far as we are aware, there is not a phrase
in the "Origin of Species" inconsistent with Professor Kölliker's position,
that "varieties arise irrespectively of the notion of purpose, or of
utility, according to general laws of Nature, and may be either useful, or
hurtful, or indifferent."
On the contrary, Mr. Darwin writes (Summary of Chap. V.):--
"Our ignorance of the laws of variation is profound. Not in one case out of
a hundred can we pretend to assign any reason why this or that part varies
more or less from the same part in the parents... The external conditions
of life, as climate and food, &c., seem to have induced some slight
modifications. Habit, in producing constitutional differences, and use, in
strengthening, and disuse, in weakening and diminishing organs, seem to
have been more potent in their effects."
And finally, as if to prevent all possible misconception, Mr. Darwin
concludes his Chapter on Variation with these pregnant words:--
"Whatever the cause may be of each slight difference in the offspring from
their parents--and a cause for each must exist--it is the steady
accumulation, through natural selection of such differences, when
beneficial to the individual, that gives rise to all the more important
modifications of structure, by which the innumerable beings on the face of
the earth are enabled to struggle with each other, and the best adapted to
survive."
We have dwelt at length upon, this subject, because of its great general
importance, and because we believe that Professor Kölliker's criticisms on
this head are based upon a misapprehension of Mr. Darwin's
views--substantially they appear to us to coincide with his own. The other
objections which Professor Kölliker enumerates and discusses are the
following: [Footnote: Space will not allow us to give Professor Kölliker's
arguments in detail; our readers will find a full and accurate version of
them in the _Reader_ for August 13th and 20th, 1864.]--
"1. No transitional forms between existing species are known; and known
varieties, whether selected or spontaneous, never go so far as to establish
new species."
To this Professor Kölliker appears to attach some weight. He makes the
suggestion that the short-faced tumbler pigeon may be a pathological
product.
"2. No transitional forms of animals are met with among the organic remains
of earlier epochs."
Upon this, Professor Kölliker remarks that the absence of transitional
forms in the fossil world, though not necessarily fatal to Darwin's views,
weakens his case.
"3. The struggle for existence does not take place."
To this objection, urged by Pelzeln, Kölliker, very justly, attaches no
weight.
"4. A tendency of organisms to give rise to useful varieties, and a natural
selection, do not exist.
"The varieties which are found arise in consequence of manifold external
influences, and it is not obvious why they all, or partially, should be
particularly useful. Each animal suffices for its own ends, is perfect of
its kind, and needs no further development. Should, however, a variety be
useful and even maintain itself, there is no obvious reason why it should
change any further. The whole conception of the imperfection of organisms
and the necessity of their becoming perfected is plainly the weakest side
of Darwin's Theory, and a _pis aller_ (Nothbehelf) because Darwin
could think of no other principle by which to explain the metamorphoses
which, as I also believe, have occurred."
Here again we must venture to dissent completely from Professor Kölliker's
conception of Mr. Darwin's hypothesis. It appears to us to be one of the
many peculiar merits of that hypothesis that it involves no belief in a
necessary and continual progress of organisms.
Again, Mr. Darwin, if we read him aright, assumes no special tendency of
organisms to give rise to useful varieties, and knows nothing of needs of
development, or necessity of perfection. What he says is, in substance: All
organisms vary. It is in the highest degree improbable that any given
variety should have exactly the same relations to surrounding conditions as
the parent stock. In that case it is either better fitted (when the
variation may be called useful), or worse fitted, to cope with them. If
better, it will tend to supplant the parent stock; if worse, it will tend
to be extinguished by the parent stock.
If (as is hardly conceivable) the new variety is so perfectly adapted to
the conditions that no improvement upon it is possible,--it will persist,
because, though it does not cease to vary, the varieties will be inferior
to itself.
If, as is more probable, the new variety is by no means perfectly adapted
to its conditions, but only fairly well adapted to them, it will persist,
so long as none of the varieties which it throws off are better adapted
than itself.
On the other hand, as soon as it varies in a useful way, _i.e._ when
the variation is such as to adapt it more perfectly to its conditions, the
fresh variety will tend to supplant the former.
So far from a gradual progress towards perfection forming any necessary
part of the Darwinian creed, it appears to us that it is perfectly
consistent with indefinite persistence in one state, or with a gradual
retrogression. Suppose, for example, a return of the glacial epoch and a
spread of polar climatal conditions over the whole globe. The operation of
natural selection under these circumstances would tend, on the whole, to
the weeding out of the higher organisms and the cherishing of the lower
forms of life. Cryptogamic vegetation would have the advantage over
Phanerogamic; _Hydrozoa_ over Corals; _Crustacea_ over
_Insecta_, and _Amphipoda_ and _Isopoda_ over the higher
_Crustacea;_ Cetaceans and Seals over the _Primates_; the
civilisation of the Esquimaux over that of the European.
"5. Pelzeln has also objected that if the later organisms have proceeded
from the earlier, the whole developmental series, from the simplest to the
highest, could not now exist; in such a case the simpler organisms must
have disappeared."
To this Professor Kölliker replies, with perfect justice, that the
conclusion drawn by Pelzeln does not really follow from Darwin's premises,
and that, if we take the facts of Paleontology as they stand, they rather
support than oppose Darwin's theory.
"6. Great weight must be attached to the objection brought forward by
Huxley, otherwise a warm supporter of Darwin's hypothesis, that we know of
no varieties which are sterile with one another, as is the rule among
sharply distinguished animal forms.
"If Darwin is right, it must be demonstrated that forms may be produced by
selection, which, like the present sharply distinguished animal forms, are
infertile, when coupled with one another, and this has not been done."
The weight of this objection is obvious; but our ignorance of the
conditions of fertility and sterility, the want of carefully conducted
experiments extending over long series of years, and the strange anomalies
presented by the results of the cross-fertilisation of many plants, should
all, as Mr. Darwin has urged, be taken into account in considering it.
The seventh objection is that we have already discussed (_supra_ p.
82).
The eighth and last stands as follows:--
"8. The developmental theory of Darwin is not needed to enable us to
understand the regular harmonious progress of the complete series of
organic forms from the simpler to the more perfect.
"The existence of general laws of Nature explains this harmony, even if we
assume that all beings have arisen separately and independent of one
another. Darwin forgets that inorganic nature, in which there can be no
thought of genetic connexion of forms, exhibits the same regular plan, the
same harmony, as the organic world; and that, to cite only one example,
there is as much a natural system of minerals as of plants and animals."
We do not feel quite sure that we seize Professor Kölliker's meaning here,
but he appears to suggest that the observation of the general order and
harmony which pervade inorganic nature, would lead us to anticipate a
similar order and harmony in the organic world. And this is no doubt true,
but it by no means follows that the particular order and harmony observed
among them should be that which we see. Surely the stripes of dun horses,
and the teeth of the _foetal_ _Balæna_, are not explained by the
"existence of General laws of Nature." Mr. Darwin endeavours to explain the
exact order of organic nature which exists; not the mere fact that there is
some order.
And with regard to the existence of a natural system of minerals; the
obvious reply is that there may be a natural classification of any
objects--of stones on a sea-beach, or of works of art; a natural
classification being simply an assemblage of objects in groups, so as to
express their most important and fundamental resemblances and differences.
No doubt Mr. Darwin believes that those resemblances and differences upon
which our natural systems or classifications of animals and plants are
based, are resemblances and differences which have been produced
genetically, but we can discover no reason for supposing that he denies the
existence of natural classifications of other kinds.
And, after all, is it quite so certain that a genetic relation may not
underlie the classification of minerals? The inorganic world has not always
been what we see it. It has certainly had its metamorphoses, and, very
probably, a long "Entwickelungsgeschichte" out of a nebular blastema. Who
knows how far that amount of likeness among sets of minerals, in virtue of
which they are now grouped into families and orders, may not be the
expression of the common conditions to which that particular patch of
nebulous fog, which may have been constituted by their atoms, and of which
they may be, in the strictest sense, the descendants, was subjected?
It will be obvious from what has preceded, that we do not agree with
Professor Kölliker in thinking the objections which he brings forward so
weighty as to be fatal to Darwin's view. But even if the case were
otherwise, we should be unable to accept the "Theory of Heterogeneous
Generation" which is offered as a substitute. That theory is thus stated:--
"The fundamental conception of this hypothesis is, that, under the
influence of a general law of development, the germs of organisms produce
others different from themselves. This might happen (1) by the fecundated
ova passing, in the course of their development, under particular
circumstances, into higher forms; (2) by the primitive and later organisms
producing other organisms without fecundation, out of germs or eggs
(Parthenogenesis)."
In favour of this hypothesis, Professor Kölliker adduces the well-known
facts of Agamogenesis, or "alternate generation"; the extreme dissimilarity
of the males and females of many animals; and of the males, females, and
neuters of those insects which live in colonies: and he defines its
relations to the Darwinian theory as follows:--
"It is obvious that my hypothesis is apparently very similar to Darwin's,
inasmuch as I also consider that the various forms of animals have
proceeded directly from one another. My hypothesis of the creation of
organisms by heterogeneous generation, however, is distinguished very
essentially from Darwin's by the entire absence of the principle of useful
variations and their natural selection: and my fundamental conception is
this, that a great plan of development lies at the foundation of the origin
of the whole organic world, impelling the simpler forms to more and more
complex developments. How this law operates, what influences determine the
development of the eggs and germs, and impel them to assume constantly new
forms, I naturally cannot pretend to say; but I can at least adduce the
great analogy of the alternation of generations. If a _Bipinnaria_, a
_Brachiolaria_, a _Pluteus_, is competent to produce the
Echinoderm, which is so widely different from it; if a hydroid polype can
produce the higher Medusa; if the vermiform Trematode 'nurse' can develop
within itself the very unlike _Cercaria_, it will not appear
impossible that the egg, or ciliated embryo, of a sponge, for once, under
special conditions, might become a hydroid polype, or the embryo of a
Medusa, an Echinoderm."
It is obvious, from, these extracts, that Professor Kölliker's hypothesis
is based upon the supposed existence of a close analogy between the
phænomena of Agamogenesis and the production of new species from
pre-existing ones. But is the analogy a real one? We think that it is not,
and, by the hypothesis cannot be.
For what are the phænomena of Agamogenesis, stated generally? An
impregnated egg develops into a sexless form, A; this gives rise,
non-sexually, to a second form or forms, B, more or less different from A.
B may multiply non-sexually again; in the simpler cases, however, it does
not, but, acquiring sexual characters, produces impregnated eggs from
whence A, once more, arises.
No case of Agamogenesis is known in which _when A differs widely from
B_, it is itself capable of sexual propagation. No case whatever is
known in which the progeny of B, by sexual generation, is other than a
reproduction of A.
But if this be a true statement of the nature of the process of
Agamogenesis, how can it enable us to comprehend the production of new
species from already existing ones? Let us suppose Hyænas to have preceded
Dogs, and to have produced the latter in this way. Then the Hyæna will
represent A, and the Dog, B. The first difficulty that presents itself is
that the Hyæna must be non-sexual, or the process will be wholly without
analogy in the world of Agamogenesis. But passing over this difficulty, and
supposing a male and female Dog to be produced at the same time from the
Hyæna stock, the progeny of the pair, if the analogy of the simpler kinds
of Agamogenesis [Footnote: If, on the contrary, we follow the analogy of
the more complex forms of Agamogenesis, such as that exhibited by some
_Trematoda_ and by the _Aphides_, the Hyæna must produce,
non-sexually, a brood of sexless Dogs, from which other sexless Dogs must
proceed. At the end of a certain number of terms of the series, the Dogs
would acquire sexes and generate young; but these young would be, not Dogs,
but Hyænas. In fact, we have demonstrated, in Agamogenetic phænomena, that
inevitable recurrence to the original type, which is asserted to be true of
variations in general, by Mr. Darwin's opponents; and which, if the
assertion could be changed into a demonstration, would, in fact, be fatal
to his hypothesis.] is to be followed, should be a litter, not of puppies,
but of young Hyænas. For the Agamogenetic series is always, as we have
seen, A:B:A:B, &c.; whereas, for the production of a new species, the
series must be A:B:B:B, &c. The production of new species, or genera, is
the extreme permanent divergence from the primitive stock. All known
Agamogenetic processes, on the other hand, end in a complete return to the
primitive stock. How then is the production of new species to be rendered
intelligible by the analogy of Agamogenesis?
The other alternative put by Professor Kölliker--the passage of fecundated
ova in the course of their development into higher forms--would, if it
occurred, be merely an extreme case of variation in the Darwinian sense,
greater in degree than, but perfectly similar in kind to, that which
occurred when the well-known Ancon Ram was developed from an ordinary Ewe's
ovum. Indeed we have always thought that Mr. Darwin has unnecessarily
hampered himself by adhering so strictly to his favourite "Natura non facit
saltum." We greatly suspect that she does make considerable jumps in the
way of variation now and then, and that these saltations give rise to some
of the gaps which appear to exist in the series of known forms.
Strongly and freely as we have ventured to disagree with Professor
Kölliker, we have always done so with regret, and we trust without
violating that respect which is due, not only to his scientific eminence
and to the careful study which he has devoted to the subject, but to the
perfect fairness of his argumentation, and the generous appreciation of the
worth of Mr. Darwin's labours which he always displays. It would be
satisfactory to be able to say as much for M. Flourens.
But the Perpetual Secretary of the French Academy of Sciences deals with
Mr. Darwin as the first Napoleon would have treated an "idéologue;" and
while displaying a painful weakness of logic and shallowness of
information, assumes a tone of authority, which always touches upon the
ludicrous, and sometimes passes the limits of good breeding.
For example (p. 56):--
"M. Darwin continue: 'Aucune distinction absolue n'a été et ne peut être
établie entre les espèces et les variétés.' Je vous ai déjà dit que vous
vous trompiez; une distinction absolue sépare les variétés d'avec les
espèces."
"_Je vous ai déjà dit_; moi, M. le Secrétaire perpétuel de l'Académie
des Sciences: et vous
"'Qui n'êtes rien,
Pas même Académicien;'
what do you mean by asserting the contrary?" Being devoid of the blessings
of an Academy in England, we are unaccustomed to see our ablest men treated
in this fashion, even by a "Perpetual Secretary."
Or again, considering that if there is any one quality of Mr. Darwin's work
to which friends and foes have alike borne witness, it is his candour and
fairness in admitting and discussing objections, what is to be thought of
M. Flourens' assertion, that
"M. Darwin ne cite que les auteurs qui partagent ses opinions." (P. 40.)
Once more (p. 65):--
"Enfin l'ouvrage de M. Darwin a paru. On ne peut qu'être frappé du talent
de l'auteur. Mais quo d'idées obscures, que d'idées fausses! Quel jargon
métaphysique jeté mal à propos dans l'histoire naturelle, qui tombe dans le
galimatias dès qu'elle sort des idées claires, des idées justes! Quel
langage prétentieux et vide! Quelles personnifications puériles et
surannées! O lucidité! 0 solidité de l'esprit Français, que devenez-vous?"
"Obscure ideas," "metaphysical jargon," "pretentious and empty language,"
"puerile and superannuated personifications." Mr. Darwin has many and hot
opponents on this side of the Channel and in Germany, but we do not
recollect to have found precisely these sins in the long catalogue of those
hitherto laid to his charge. It is worth while, therefore, to examine into
these discoveries effected solely by the aid of the "lucidity and solidity"
of the mind of M. Flourens.
According to M. Flourens, Mr. Darwin's great error is that he has
personified Nature (p. 10), and further that he has
"imagined a natural selection: he imagines afterwards that this power of
selecting (_pouvoir d'élire_) which he gives to Nature is similar to
the power of man. These two suppositions admitted, nothing stops him: he
plays with Nature as he likes, and makes her do all he pleases." (P. 6.)
And this is the way M. Flourens extinguishes natural selection:
"Voyons donc encore une fois, ce qu'il peut y avoir de fondé dans ce qu'on
nomme _élection naturelle_.
"_L'élection naturelle_ n'est sous un autre nom que la nature. Pour un
être organisé, la nature n'est que l'organisation, ni plus ni moins.
"Il faudra donc aussi personnifier _l'organisation,_ et dire que
_l'organisation_ choisit _l'organisation. L'élection naturelle_
est cette _forme substantielle_ dont on jouait autrefois avec tant de
facilité. Aristote disait que 'Si l'art de bâtir était dans le bois, cet
art agirait comme la nature.' A la place de _l'art de bâtir_ M. Darwin
met _l'élection naturelle,_ et c'est tout un: l'un n'est pas plus
chimérique que l'autre." (P. 31.)
And this is really all that M. Flourens can make of Natural Selection. We
have given the original, in fear lest a translation should be regarded as a
travesty; but with the original before the reader, we may try to analyse
the passage. "For an organised being, Nature is only organisation, neither
more nor less."
Organised beings then have absolutely no relation to inorganic nature: a
plant does not depend on soil or sunshine, climate, depth in the ocean,
height above it; the quantity of saline matters in water have no influence
upon animal life; the substitution of carbonic acid for oxygen in our
atmosphere would hurt nobody! That these are absurdities no one should know
better than M. Flourens; but they are logical deductions from the assertion
just quoted, and from the further statement that natural selection means
only that "organisation chooses and selects organisation."
For if it be once admitted (what no sane man denies) that the chances of
life of any given organism are increased by certain conditions (A) and
diminished by their opposites (B), then it is mathematically certain that
any change of conditions in the direction of (A) will exercise a selective
influence in favour of that organism, tending to its increase and
multiplication, while any change in the direction of (B) will exercise a
selective influence against that organism, tending to its decrease and
extinction.
Or, on the other hand, conditions remaining the same, let a given organism
vary (and no one doubts that they do vary) in two directions: into one form
(_a_) better fitted to cope with these conditions than the original
stock, and a second (_b_) less well adapted to them. Then it is no
less certain that the conditions in question must exercise a selective
influence in favour of (_a_) and against (_b_), so that
(_a_) will tend to predominance, and (_b_) to extirpation.
That M. Flourens should be unable to perceive the logical necessity of
these simple arguments, which lie at the foundation of all Mr. Darwin's
reasoning; that he should confound an irrefragable deduction from the
observed relations of organisms to the conditions which lie around them,
with a metaphysical "forme substantielle," or a chimerical personification
of the powers of Nature, would be incredible, were it not that other
passages of his work leave no room for doubt upon the subject.
"On imagine une _élection naturelle_ que, pour plus de ménagement, on
me dit être _inconsciente_, sans s'apercevoir que le contresens
littéral est précisément là: _élection inconsciente_." (P. 52.)
"J'ai déjà dit ce qu'il faut penser de _l'élection naturelle_. Ou
_l'élection naturelle_ n'est rien, ou c'est la nature: mais la nature
douée _d'élection_, mais la nature personnifiée: dernière erreur du
dernier siècle: Le XIXe ne fait plus de personnifications." (P. 53.)
M. Flourens cannot imagine an unconscious selection--it is for him a
contradiction in terms. Did M. Flourens ever visit one of the prettiest
watering-places of "la belle France," the Baie d'Arcachon? If so, he will
probably have passed through the district of the Landes, and will have had
an opportunity of observing the formation of "dunes" on a grand scale. What
are these "dunes"? The winds and waves of the Bay of Biscay have not much
consciousness, and yet they have with great care "selected," from among an
infinity of masses of silex of all shapes and sizes, which have been
submitted to their action, all the grains of sand below a certain size, and
have heaped them by themselves over a great area. This sand has been
"unconsciously selected" from amidst the gravel in which it first lay with
as much precision as if man had "consciously selected" it by the aid of a
sieve. Physical Geology is full of such selections--of the picking out of
the soft from the hard, of the soluble from the insoluble, of the fusible
from the infusible, by natural agencies to which we are certainly not in
the habit of ascribing consciousness.
But that which wind and sea are to a sandy beach, the sum of influences,
which we term the "conditions of existence," is to living organisms. The
weak are sifted out from the strong. A frosty night "selects" the hardy
plants in a plantation from among the tender ones as effectually as if it
were the wind, and they, the sand and pebbles, of our illustration; or, on
the other hand, as if the intelligence of a gardener had been operative in
cutting the weaker organisms down. The thistle, which has spread over the
Pampas, to the destruction of native plants, has been more effectually
"selected" by the unconscious operation of natural conditions than if a
thousand agriculturists had spent their time in sowing it.
It is one of Mr. Darwin's many great services to Biological science that he
has demonstrated the significance of these facts. He has shown that given
variation and given change of conditions the inevitable result is the
exercise of such an influence upon organisms that one is helped and another
is impeded; one tends to predominate, another to disappear; and thus the
living world bears within itself, and is surrounded by, impulses towards
incessant change.
But the truths just stated are as certain as any other physical laws, quite
independently of the truth, or falsehood, of the hypothesis which Mr.
Darwin has based upon them; and that Mr. Flourens, missing the substance
and grasping at a shadow, should be blind to the admirable exposition of
them, which Mr. Darwin has given, and see nothing there but a "dernière
erreur du dernier siècle"--a personification of Nature--leads us indeed to
cry with him: "O lucidité! O solidité de l'esprit Français, que
devenez-vous?"
M. Flourens has, in fact, utterly failed to comprehend the first principles
of the doctrine which he assails so rudely. His objections to details are
of the old sort, so battered and hackneyed on this side of the Channel,
that not even a Quarterly Reviewer could be induced to pick them up for the
purpose of pelting Mr. Darwin over again. We have Cuvier and the mummies;
M. Roulin and the domesticated animals of America; the difficulties
presented by hybridism and by Palæontology; Darwinism a
_rifacciamento_ of De Maillet and Lamarck; Darwinism a system without
a commencement, and its author bound to believe in M. Pouchet, &c. &c. How
one knows it all by heart, and with what relief one reads at p. 65--
"Je laisse M. Darwin!"
But we cannot leave M. Flourens without calling our readers' attention to
his wonderful tenth chapter, "De la Préexistence des Germes et de
l'Epigénèse," which opens thus:--
"Spontaneous generation is only a chimaera. This point established, two
hypotheses remain: that of _pre-existence_ and that of
_epigenesis_. The one of these hypotheses has as little foundation as
the other." (p. 163.)
"The doctrine of _epigenesis_ is derived from Harvey: following by
ocular inspection the development of the new being in the Windsor does, he
saw each part appear successively, and taking the moment of
_appearance_ for the moment of _formation_ he imagined
_epigenesis_." (p. 165.)
On the contrary, says M. Flourens (p. 167),
"The new being is formed at a stroke (_tout d'un coup_), as a whole,
instantaneously; it is not formed part by part, and at different times. It
is formed at once at the single _individual_ moment at which the
conjunction of the male and female elements takes place."
It will be observed that M. Flourens uses language which cannot be
mistaken. For him, the labours of Von Baer, of Rathke, of Coste, and their
contemporaries and successors in Germany, France, and England, are
non-existent: and, as Darwin "_imagina_" natural selection, so Harvey
"_imagina_" that doctrine which gives him an even greater claim to the
veneration of posterity than his better known discovery of the circulation
of the blood.
Language such as that we have quoted is, in fact, so preposterous, so
utterly incompatible with anything but absolute ignorance of some of the
best established facts, that we should have passed it over in silence had
it not appeared to afford some clue to M. Flourens' unhesitating, _ à
priori_, repudiation of all forms of the doctrine of progressive
modification of living beings. He whose mind remains uninfluenced by an
acquaintance with the phænomena of development, must indeed lack one of the
chief motives towards the endeavour to trace a genetic relation between the
different existing forms of life. Those who are ignorant of Geology, find
no difficulty in believing that the world was made as it is; and the
shepherd, untutored in history, sees no reason to regard the green mounds
which indicate the site of a Roman camp as aught but part and parcel of the
primæval hillside. So M. Flourens, who believes that embryos are formed
"tout d'un coup," naturally finds no difficulty in conceiving that species
came into existence in the same way.
IV
THE GENEALOGY OF ANIMALS [Footnote: _The Natural History of Creation_.
By Dr. Ernst Haeckel. [_Natürliche Schöpfungs-Geschichte_.--Von Dr.
Ernst Haeckel, Professor an der Universität Jena.] Berlin, 1868.]
[1869]
Considering that Germany now takes the lead of the world in scientific
investigation, and particularly in biology, Mr. Darwin must be well pleased
at the rapid spread of his views among some of the ablest and most
laborious of German naturalists.
Among these, Professor Haeckel, of Jena, is the Coryphæus. I know of no
more solid and important contributions to biology in the past seven years
than Haeckel's work on the "Radiolaria," and the researches of his
distinguished colleague Gegenbaur, in vertebrate anatomy; while in
Haeckel's "Generelle Morphologie" there is all the force, suggestiveness,
and, what I may term the systematising power, of Oken, without his
extravagance. The "Generelle Morphologie" is, in fact, an attempt to put
the Doctrine of Evolution, so far as it applies to the living world, into a
logical form; and to work out its practical applications to their final
results. The work before, us, again, may be said to be an exposition of the
"Generelle Morphologie" for an educated public, consisting, as it does, of
the substance of a series of lectures delivered before a mixed audience at
Jena, in the session 1867-8.
"The Natural History of Creation,"--or, as Professor Haeckel admits it
would have been better to call his work, "The History of the Development or
Evolution of Nature,"--deals, in the first six lectures, with the general
and historical aspects of the question and contains a very interesting and
lucid account of the views of Linnæus, Cuvier, Agassiz, Goethe, Oken, Kant,
Lamarck, Lyell, and Darwin, and of the historical filiation of these
philosophers.
The next six lectures are occupied by a well-digested statement of Mr.
Darwin's views. The thirteenth lecture discusses two topics which are not
touched by Mr. Darwin, namely, the origin of the present form of the solar
system, and that of living matter. Full justice is done to Kant, as the
originator of that "cosmic gas theory," as the Germans somewhat quaintly
call it, which is commonly ascribed to Laplace. With respect to spontaneous
generation, while admitting that there is no experimental evidence in its
favour, Professor Haeckel denies the possibility of disproving it, and
points out that the assumption that it has occurred is a necessary part of
the doctrine of Evolution. The fourteenth lecture, on "Schöpfungs-Perioden
und Schöpfungs-Urkunden," answers pretty much to the famous disquisition on
the "Imperfection of the Geological Record" in the "Origin of Species."
The following five lectures contain the most original matter of any, being
devoted to "Phylogeny," or the working out of the details of the process of
Evolution in the animal and vegetable kingdoms, so as to prove the line of
descent of each group of living beings, and to furnish it with its proper
genealogical tree, or "phylum."
The last lecture considers objections and sums up the evidence in favour of
biological Evolution.
I shall best testify to my sense of the value of the work thus briefly
analysed if I now proceed to note down some of the more important
criticisms which have been suggested to me by its perusal.
I. In more than one place, Professor Haeckel enlarges upon the service
which the "Origin of Species" has done, in favouring what he terms the
"causal or mechanical" view of living nature as opposed to the
"teleological or vitalistic" view. And no doubt it is quite true that the
doctrine of Evolution is the most formidable opponent of all the commoner
and coarser forms of Teleology. But perhaps the most remarkable service to
the philosophy of Biology rendered by Mr. Darwin is the reconciliation of
Teleology and Morphology, and the explanation of the facts of both which
his views offer.
The Teleology which supposes that the eye, such as we see it in man or one
of the higher _Vertebrata_, was made with the precise structure which
it exhibits, for the purpose of enabling the animal which possesses it to
see, has undoubtedly received its death-blow. Nevertheless it is necessary
to remember that there is a wider Teleology, which is not touched by the
doctrine of Evolution, but is actually based upon the fundamental
proposition of Evolution. That proposition is, that the whole world, living
and not living, in the result of the mutual interaction, according to
definite laws, of the forces possessed by the molecules of which the
primitive nebulosity of the universe was composed. If this be true, it is
no less certain that the existing world lay, potentially, in the cosmic
vapour; and that a sufficient intelligence could, from a knowledge of the
properties of the molecules of that vapour, have predicted, say the state
of the Fauna of Britain in 1869, with as much certainty as one can say what
will happen to the vapour of the breath in a cold winter's day.
Consider a kitchen clock, which ticks loudly, shows the hours, minutes, and
seconds, strikes, cries "cuckoo!" and perhaps shows the phases of the moon.
When the clock is wound up, all the phenomena which it exhibits are
potentially contained in its mechanism, and a clever clockmaker could
predict all it will do after an examination of its structure.
If the evolution theory is correct, the molecular structure of the cosmic
gas stands in the same relation to the phenomena of the world as the
structure of the clock to its phenomena.
Now let us suppose a death-watch, living in the clock-case, to be a learned
and intelligent student of its works. He might say, "I find here nothing
but matter and force and pure mechanism from beginning to end," and he
would be quite right. But if he drew the conclusion that the clock was not
contrived for a purpose, he would be quite wrong. On the other hand,
imagine another death-watch of a different turn of mind. He, listening to
the monotonous "tick! tick!" so exactly like his own, might arrive at the
conclusion that the clock was itself a monstrous sort of death-watch, and
that its final cause and purpose was to tick. How easy to point to the
clear relation of the whole mechanism to the pendulum, to the fact that the
one thing the clock did always and without intermission was to tick, and
that all the rest of its phenomena were intermittent and subordinate to
ticking! For all this, it is certain that kitchen clocks are not contrived
for the purpose of making a ticking noise.
Thus the teleological theorist would be as wrong as the mechanical
theorist, among our death-watches; and, probably, the only death-watch who
would be right would be the one who should maintain that the sole thing
death-watches could be sure about was the nature of the clock-works and the
way they move; and that the purpose of the clock lay wholly beyond the
purview of beetle faculties.
Substitute "cosmic vapour" for "clock," and "molecules" for "works," and
the application of the argument is obvious. The teleological and the
mechanical views of nature are not, necessarily, mutually exclusive. On the
contrary, the more purely a mechanist the speculator is, the more firmly
does he assume a primordial molecular arrangement, of which all the
phenomena of the universe are the consequences; and the more completely is
he thereby at the mercy of the teleologist, who can always defy him to
disprove that this primordial molecular arrangement was not intended to
evolve the phenomena of the universe. On the other hand, if the teleologist
assert that this, that, or the other result of the working of any part of
the mechanism of the universe is its purpose and final cause, the mechanist
can always inquire how he knows that it is more than an unessential
incident--the mere ticking of the clock, which he mistakes for its
function. And there seems to be no reply to this inquiry, any more than to
the further, not irrational, question, why trouble one's self about matters
which are out of reach, when the working of the mechanism itself, which is
of infinite practical importance, affords scope for all our energies?
Professor Haeckel has invented a new and convenient name "Dysteleology,"
for the study of the "purposelessnesses" which are observable in living
organisms--such as the multitudinous cases of rudimentary and apparently
useless structures. I confess, however, that it has often appeared to me
that the facts of Dysteleology cut two ways. If we are to assume, as
evolutionists in general do, that useless organs atrophy, such cases as the
existence of lateral rudiments of toes, in the foot of a horse, place us in
a dilemma. For, either these rudiments are of no use to the animal, in
which case, considering that the horse has existed in its present form
since the Pliocene epoch, they surely ought to have disappeared; or they
are of some use to the animal, in which case they are of no use as
arguments against Teleology. A similar, but still stronger, argument may be
based upon the existence of teats, and even functional mammary glands, in
male mammals. Numerous cases of "Gynæcomasty," or functionally active
breasts in men, are on record, though there is no mammalian species
whatever in which the male normally suckles the young. Thus, there can be
little doubt that the mammary gland was as apparently useless in the
remotest male mammalian ancestor of man as in living men, and yet it has
not disappeared. Is it then still profitable to the male organism to retain
it? Possibly; but in that case its dysteleological value is gone.
[Footnote: The recent discovery of the important part played by the Thyroid
gland should be a warning to all speculators about useless organs. 1893.]
II. Professor Haeckel looks upon the causes which have led to the present
diversity of living nature as twofold. Living matter, he tells us, is urged
by two impulses: a centripetal, which tends to preserve and transmit the
specific form, and which he identifies with heredity; and a centrifugal,
which results from the tendency of external conditions to modify the
organism and effect its adaptation to themselves. The internal impulse is
conservative, and tends to the preservation of specific, or individual,
form; the external impulse is metamorphic, and tends to the modification of
specific, or individual, form.
In developing his views upon this subject, Professor Haeckel introduces
qualifications which disarm some of the criticisms I should have been
disposed to offer; but I think that his method of stating the case has the
inconvenience of tending to leave out of sight the important fact--which is
a cardinal point in the Darwinian hypothesis--that the tendency to vary, in
a given organism, may have nothing to do with the external conditions to
which that individual organism is exposed, but may depend wholly upon
internal conditions. No one, I imagine, would dream of seeking for the
cause of the development of the sixth finger and toe in the famous Maltese,
in the direct influence of the external conditions of his life.
I conceive that both hereditary transmission and adaptation need to be
analysed into their constituent conditions by the further application of
the doctrine of the Struggle for Existence. It is a probable hypothesis,
that what the world is to organisms in general, each organism is to the
molecules of which it is composed. Multitudes of these, having diverse
tendencies, are competing with one another for opportunity to exist and
multiply; and the organism, as a whole, is as much the product of the
molecules which are victorious as the Fauna, or Flora, of a country is the
product of the victorious organic beings in it.
On this hypothesis, hereditary transmission is the result of the victory of
particular molecules contained in the impregnated germ. Adaptation to
conditions is the result of the favouring of the multiplication of those
molecules whose organising tendencies are most in harmony with such
conditions. In this view of the matter, conditions are not actively
productive, but are passively permissive; they do not cause variation in
any given direction, but they permit and favour a tendency in that
direction which already exists.
It is true that, in the long run, the origin of the organic molecules
themselves, and of their tendencies, is to be sought in the external world;
but if we carry our inquiries as far back as this, the distinction between
internal and external impulses vanishes. On the other hand, if we confine
ourselves to the consideration of a single organism, I think it must be
admitted that the existence of an internal metamorphic tendency must be as
distinctly recognised as that of an internal conservative tendency; and
that the influence of conditions is mainly, if not wholly, the result of
the extent to which they favour the one, or the other, of these tendencies.
III. There is only one point upon which I fundamentally and entirely
disagree with Professor Haeckel, but that is the very important one of his
conception of geological time, and of the meaning of the stratified rocks
as records and indications of that time. Conceiving that the stratified
rocks of an epoch indicate a period of depression, and that the intervals
between the epochs correspond with periods of elevation of which we have no
record, he intercalates between the different epochs, or periods, intervals
which he terms "Ante-periods." Thus, instead of considering the Triassic,
Jurassic, Cretaceous, and Eocene periods, as continuously successive, he
interposes a period before each, as an "Antetrias-zeit," "Antejura-zeit,"
"Antecreta-zeit," "Anteo-cenzeit," &c. And he conceives that the abrupt
changes between the Faunæ of the different formations are due to the lapse
of time, of which we have no organic record, during their "Ante-periods."
The frequent occurrence of strata containing assemblages of organic forms
which are intermediate between those of adjacent formations, is, to my
mind, fatal to this view. In the well-known St. Cassian beds, for example,
Palaeozoic and Mesozoic forms are commingled, and, between the Cretaceous
and the Eocene formations, there are similar transitional beds. On the
other hand, in the middle of the Silurian series, extensive unconformity of
the strata indicates the lapse of vast intervals of time between the
deposit of successive beds, without any corresponding change in the Fauna.
Professor Haeckel will, I fear, think me unreasonable, if I say that he
seems to be still overshadowed by geological superstitions; and that he
will have to believe in the completeness of the geological record far less
than he does at present. He assumes, for example, that there was no dry
land, nor any terrestrial life, before the end of the Silurian epoch,
simply because, up to the present time, no indications of fresh water, or
terrestrial organisms, have been found in rocks of older date. And, in
speculating upon the origin of a given group, he rarely goes further back
than the "Ante-period," which precedes that in which the remains of animals
belonging to that group are found. Thus, as fossil remains of the majority
of the groups of _Reptilia_ are first found in the Trias, they are
assumed to have originated in the "Antetriassic" period, or between the
Permian and Triassic epochs.
I confess this is wholly incredible to me. The Permian and the Triassic
deposits pass completely into one another; there is no sort of
discontinuity answering to an unrecorded "Antetrias"; and, what is more, we
have evidence of immensely extensive dry land during the formation of these
deposits. We know that the dry land of the Trias absolutely teemed with
reptiles of all groups except Pterodactyles, Snakes, and perhaps Tortoises;
there is every probability that true Birds existed, and _Mammalia_
certainly did. Of the inhabitants of the Permian dry land, on the contrary,
all that have left a record are a few lizards. Is it conceivable that these
last should really represent the whole terrestrial population of that time,
and that the development of Mammals, of Birds, and of the highest forms of
Reptiles, should have been crowded into the time during which the Permian
conditions quietly passed away, and the Triassic conditions began? Does not
any such supposition become in the highest degree improbable, when, in the
terrestrial or fresh-water Labyrinthodonts, which lived on the land of the
Carboniferous epoch, as well as on that of the Trias, we have evidence that
one form of terrestrial life persisted, throughout all these ages, with no
important modification? For my part, having regard to the small amount of
modification (except in the way of extinction) which the Crocodilian,
Lacertilian, and Chelonian _Reptilia_ have undergone, from the older
Mesozoic times to the present day, I cannot but put the existence of the
common stock from which they sprang far back in the Palæozoic epoch; and I
should apply a similar argumentation to all other groups of animals.
[The remainder of this essay contains a discussion of questions of taxonomy
and phylogeny, which is now antiquated. I have reprinted the considerations
about the reconciliation of Teleology with Morphology, about
"Dysteleology," and about the struggle for existence within the organism,
because it has happened to me to be charged with overlooking them.
In discussing Teleology, I ought to have pointed out, as I have done
elsewhere (_Life and Letters of Charles Darwin_, vol. ii. p. 202),
that Paley "proleptically accepted the modern doctrine of Evolution,"
(_Natural Theology_, chap. xxiii.). 1893.]
V
MR. DARWIN'S CRITICS [Footnote: _Contributions to the Theory of Natural
Selection_. By A. R. Wallace. 1870.--2. _The Genesis of Species_.
By St. George Mivart, F.R.S. Second Edition. 1871.--3. _Darwin's Descent
of Man_. Quarterly Review, July 1871.]
[1871]
The gradual lapse of time has now separated us by more than a decade from
the date of the publication of the "Origin of Species"--and whatever may be
thought or said about Mr. Darwin's doctrines, or the manner in which he has
propounded them, this much is certain, that, in a dozen years, the "Origin
of Species" has worked as complete a revolution in biological science as
the "Principia" did in astronomy--and it has done so, because, in the words
of Helmholtz, it contains "an essentially new creative thought." [Footnote:
Helmholtz: _Ueber das Ziel und die Fortschritte der
Naturwissenschaft_. Eröffnungsrede für die Naturforscherversammlung zu
Innsbruck. 1869.] And as time has slipped by, a happy change has come over
Mr. Darwin's critics. The mixture of ignorance and insolence which, at
first, characterised a large proportion of the attacks with which he was
assailed, is no longer the sad distinction of anti-Darwinian criticism.
Instead of abusive nonsense, which merely discredited its writers, we read
essays, which are, at worst, more or less intelligent and appreciative;
while, sometimes, like that which appeared in the "North British Review"
for 1867, they have a real and permanent value.
The several publications of Mr. Wallace and Mr. Mivart contain discussions
of some of Mr. Darwin's views, which are worthy of particular attention,
not only on account of the acknowledged scientific competence of these
writers, but because they exhibit an attention to those philosophical
questions which underlie all physical science, which is as rare as it is
needful. And the same may be said of an article in the "Quarterly Review"
for July 1871, the comparison of which with an article in the same Review
for July 1860, is perhaps the best evidence which can be brought forward of
the change which has taken place in public opinion on "Darwinism."
The Quarterly Reviewer admits "the certainty of the action of natural
selection" (p. 49); and further allows that there is an _à priori_
probability in favour of the evolution of man from some lower animal form,
if these lower animal forms themselves have arisen by evolution.
Mr. Wallace and Mr. Mivart go much further than this. They are as stout
believers in evolution as Mr. Darwin himself; but Mr. Wallace denies that
man can have been evolved from a lower animal by that process of natural
selection which he, with Mr. Darwin, holds to have been sufficient for the
evolution of all animals below man; while Mr. Mivart, admitting that
natural selection has been one of the conditions of the evolution of the
animals below man, maintains that natural selection must, even in their
case, have been supplemented by "some other cause"--of the nature of which,
unfortunately, he does not give us any idea. Thus Mr. Mivart is less of a
Darwinian than Mr. Wallace, for he has less faith in the power of natural
selection. But he is more of an evolutionist than Mr. Wallace, because Mr.
Wallace thinks it necessary to call in an intelligent agent--a sort of
supernatural Sir John Sebright--to produce even the animal frame of man;
while Mr. Mivart requires no Divine assistance till he comes to man's soul.
Thus there is a considerable divergence between Mr. Wallace and Mr. Mivart.
On the other hand, there are some curious similarities between Mr. Mivart
and the Quarterly Reviewer, and these are sometimes so close, that, if Mr.
Mivart thought it worth while, I think he might make out a good case of
plagiarism against the Reviewer, who studiously abstains from quoting him.
Both the Reviewer and Mr. Mivart reproach Mr. Darwin with being, "like so
many other physicists," entangled in a radically false metaphysical system,
and with setting at nought the first principles of both philosophy and
religion. Both enlarge upon the necessity of a sound philosophical basis,
and both, I venture to add, make a conspicuous exhibition of its absence.
The Quarterly Reviewer believes that man "differs more from an elephant or
a gorilla than do these from the dust of the earth on which they tread,"
and Mr. Mivart has expressed the opinion that there is more difference
between man and an ape than there is between an ape and a piece of granite.
[Footnote: See the _Tablet_ for March 11, 1871.]
And even when Mr. Mivart (p. 86) trips in a matter of anatomy, and creates
a difficulty for Mr. Darwin out of a supposed close similarity between the
eyes of fishes and cephalopods, which (as Gegenbaur and others have clearly
shown) does not exist, the Quarterly Reviewer adopts the argument without
hesitation (p. 66).
There is another important point, however, in which it is hard to say
whether Mr. Mivart diverges from the Quarterly Reviewer or not.
The Reviewer declares that Mr. Darwin has, "with needless opposition, set
at nought the first principles of both philosophy and religion" (p. 90).
It looks, at first, as if this meant, that Mr. Darwin's views being false,
the opposition to "religion" which flows from them must be needless. But I
suspect this is not the right view of the meaning of the passage, as Mr.
Mivart, from whom the Quarterly Reviewer plainly draws so much inspiration,
tells us that "the consequences which have been drawn from evolution,
whether exclusively Darwinian or not, to the prejudice of religion, by no
means follow from it, and are in fact illegitimate" (p. 5).
I may assume, then, that the Quarterly Reviewer and Mr. Mivart admit that
there is no necessary opposition between "evolution whether exclusively
Darwinian or not," and religion. But then, what do they mean by this last
much-abused term? On this point the Quarterly Reviewer is silent. Mr.
Mivart, on the contrary, is perfectly explicit, and the whole tenor of his
remarks leaves no doubt that by "religion" he means theology; and by
theology, that particular variety of the great Proteus, which is expounded
by the doctors of the Roman Catholic Church, and held by the members of
that religious community to be the sole form of absolute truth and of
saving faith.
According to Mr. Mivart, the greatest and most orthodox authorities upon
matters of Catholic doctrine agree in distinctly asserting "derivative
creation" or evolution; "and thus their teachings harmonise with all that
modern science can possibly require" (p. 305).
I confess that this bold assertion interested me more than anything else in
Mr. Mivart's book. What little knowledge I possessed of Catholic doctrine,
and of the influence exerted by Catholic authority in former times, had not
led me to expect that modern science was likely to find a warm welcome
within the pale of the greatest and most consistent of theological
organisations.
And my astonishment reached its climax when I found Mr. Mivart citing
Father Suarez as his chief witness in favour of the scientific freedom
enjoyed by Catholics--the popular repute of that learned theologian and
subtle casuist not being such as to make his works a likely place of refuge
for liberality of thought. But in these days, when Judas Iscariot and
Robespierre, Henry VIII. and Catiline, have all been shown to be men of
admirable virtue, far in advance of their age, and consequently the victims
of vulgar prejudice, it was obviously possible that Jesuit Suarez might be
in like case. And, spurred by Mr. Mivart's unhesitating declaration, I
hastened to acquaint myself with such of the works of the great Catholic
divine as bore upon the question, hoping, not merely to acquaint myself
with the true teachings of the infallible Church, and free myself of an
unjust prejudice; but, haply, to enable myself, at a pinch, to put some
Protestant bibliolater to shame, by the bright example of Catholic freedom
from the trammels of verbal inspiration.
I regret to say that my anticipations have been cruelly disappointed. But
the extent to which my hopes have been crushed can only be fully
appreciated by citing, in the first place, those passages of Mr. Mivart's
work by which they were excited. In his introductory chapter I find the
following passages:--
"The prevalence of this theory [of evolution] need alarm no one, for it is,
without any doubt, perfectly consistent with the strictest and most
orthodox Christian [Footnote: It should be observed that Mr. Mivart employs
the term 'Christian' as if it were the equivalent of 'Catholic.'] theology"
(p. 5).
"Mr. Darwin and others may perhaps be excused if they have not devoted much
time to the study of Christian philosophy; but they have no right to assume
or accept without careful examination, as an unquestioned fact, that in
that philosophy there is a necessary antagonism between the two ideas
'creation' and 'evolution,' as applied to organic forms.
"It is notorious and patent to all who choose to seek, that many
distinguished Christian thinkers have accepted, and do accept, both ideas,
_i.e._ both 'creation' and 'evolution.'
"As much as ten years ago an eminently Christian writer observed: 'The
creationist theory does not necessitate the perpetual search after
manifestations of miraculous power and perpetual "catastrophes." Creation
is not a miraculous interference with the laws of Nature, but the very
institution of those laws. Law and regularity, not arbitrary intervention,
was the patristic ideal of creation. With this notion they admitted,
without difficulty, the most surprising origin of living creatures,
provided it took place by _law_. They held that when God said, "Let
the waters produce," "Let the earth produce," He conferred forces on the
elements of earth and water which enabled them naturally to produce the
various species of organic beings. This power, they thought, remains
attached to the elements throughout all time.' The same writer quotes St.
Augustin and St. Thomas Aquinas, to the effect that, 'in the institution of
Nature, we do not look for miracles, but for the laws of Nature.' And,
again, St. Basil speaks of the continued operation of natural laws in the
production of all organisms.
"So much for the writers of early and mediæval times. As to the present
day, the author can confidently affirm that there are many as well versed
in theology as Mr. Darwin is in his own department of natural knowledge,
who would not be disturbed by the thorough demonstration of his theory.
Nay, they would not even be in the least painfully affected at witnessing
the generation of animals of complex organisation by the skilful artificial
arrangement of natural forces, and the production, in the future, of a fish
by means analogous to those by which we now produce urea.
"And this because they know that the possibility of such phenomena, though
by no means actually foreseen, has yet been fully provided for in the old
philosophy centuries before Darwin, or even centuries before Bacon, and
that their place in the system can be at once assigned them without even
disturbing its order or marring its harmony.
"Moreover, the old tradition in this respect has never been abandoned,
however much it may have been ignored or neglected by some modern writers.
In proof of this, it may be observed that perhaps no post-mediæval
theologian has a wider reception amongst Christians throughout the world
than Suarez, who has a separate section [Footnote: Suarez,
_Metaphysica_. Edition Vivés. Paris, 1868, vol. i Disput. xv. § 2.] in
opposition to those who maintain the distinct creation of the various
kinds--or substantial forms--of organic life" (pp. 19-21).
Still more distinctly does Mr. Mivart express himself in the same sense, in
his last chapter, entitled "Theology and Evolution" (pp. 302-5).
"It appears, then, that Christian thinkers are perfectly free to accept the
general evolution theory. But are there any theological authorities to
justify this view of the matter?
"Now, considering how extremely recent are these biological speculations,
it might hardly be expected _à priori_ that writers of earlier ages
should have given expression to doctrines harmonising in any degree with
such very modern views; nevertheless, this is certainly the case, and it
would be easy to give numerous examples. It will be better, however, to
cite one or two authorities of weight. Perhaps no writer of the earlier
Christian ages could be quoted whose authority is more generally recognised
than that of St. Augustin. The same may be said of the mediæval period for
St. Thomas Aquinas: and since the movement of Luther, Suarez may be taken
as an authority, widely venerated, and one whose orthodoxy has never been
questioned.
"It must be borne in mind that for a considerable time even after the last
of these writers no one had disputed the generally received belief as to
the small age of the world, or at least of the kinds of animals and plants
inhabiting it. It becomes, therefore, much more striking if views formed
under such a condition of opinion are found to harmonise with modern ideas
concerning 'Creation' and organic Life.
"Now St. Augustin insists in a very remarkable manner on the merely
derivative sense in which God's creation of organic forms is to be
understood; that is, that God created them by conferring on the material
world the power to evolve them under suitable conditions."
Mr. Mivart then cites certain passages from St. Augustin, St. Thomas
Aquinas, and Cornelius à Lapide, and finally adds:--
"As to Suarez, it will be enough to refer to Disp. xv. sec. 2, No. 9, p.
508, t. i. edition Vivés, Paris; also Nos. 13-15. Many other references to
the same effect could easily be given, but these may suffice.
"It is then evident that ancient and most venerable theological authorities
distinctly assert derivative creation, and thus their teachings harmonise
with all that modern science can possibly require."
It will be observed that Mr. Mivart refers solely to Suarez's fifteenth
Disputation, though he adds, "Many other references to the same effect
could easily be given." I shall look anxiously for these references in the
third edition of the "Genesis of Species." For the present, all I can say
is, that I have sought in vain, either in the fifteenth Disputation, or
elsewhere, for any passage in Suarez's writings which, in the slightest
degree, bears out Mr. Mivart's views as to his opinions. [Footnote: The
edition of Suarez's _Disputationes_ from which the following citations
are given, is Birckmann's, in two volumes folio, and is dated 1680.]
The title of this fifteenth Disputation is "De causa formali substantiali,"
and the second section of that Disputation (to which Mr. Mivart refers) is
headed, "Quomodo possit forma substantialis fieri in materia et ex
materia?"
The problem which Suarez discusses in this place may be popularly stated
thus: According to the scholastic philosophy every natural body has two
components--the one its "matter" (_materia prima_), the other its
"substantial form" (_forma substantialis_). Of these the matter is
everywhere the same, the matter of one body being indistinguishable from
the matter of any other body. That which differentiates any one natural
body from all others is its substantial form, which inheres in the matter
of that body, as the human soul inheres in the matter of the frame of man,
and is the source of all the activities and other properties of the body.
Thus, says Suarez, if water is heated, and the source of heat is then
removed, it cools again. The reason of this is that there is a certain
"_intimius principium_" in the water, which brings it back to the cool
condition when the external impediment to the existence of that condition
is removed. This _intimius principium_ is the "substantial form" of
the water. And the substantial form of the water is not only the cause
(_radix_) of the coolness of the water, but also of its moisture, of
its density, and of all its other properties.
It will thus be seen that "substantial forms" play nearly the same part in
the scholastic philosophy as "forces" do in modern science; the general
tendency of modern thought being to conceive all bodies as resolvable into
material particles and forces, in virtue of which last these particles
assume those dispositions and exercise those powers which are
characteristic of each particular kind of matter.
But the Schoolmen distinguished two kinds of substantial forms, the one
spiritual and the other material. The former division is represented by the
human soul, the _anima rationalis_; and they affirm as a matter, not
merely of reason, but of faith, that every human soul is created out of
nothing, and by this act of creation is endowed with the power of existing
for all eternity, apart from the _materia prima_ of which the
corporeal frame of man is composed. And the _anima rationalis_, once
united with the _materia prima_ of the body, becomes its substantial
form, and is the source of all the powers and faculties of man--of all the
vital and sensitive phenomena which he exhibits--just as the substantial
form of water is the source of all its qualities.
The "material substantial forms" are those which inform all other natural
bodies except that of man; and the object of Suarez in the present
Disputation, is to show that the axiom "_ex nihilo nihil fit_," though
not true of the substantial form of man, is true of the substantial forms
of all other bodies, the endless mutations of which constitute the ordinary
course of nature. The origin of the difficulty which he discusses is easily
comprehensible. Suppose a piece of bright iron to be exposed to the air.
The existence of the iron depends on the presence within it of a
substantial form, which is the cause of its properties, _e.g._
brightness, hardness, weight. But, by degrees, the iron becomes converted
into a mass of rust, which is dull, and soft, and light, and, in all other
respects, is quite different from the iron. As, in the scholastic view,
this difference is due to the rust being informed by a new substantial
form, the grave problem arises, how did this new substantial form come into
being? Has it been created? or has it arisen by the power of natural
causation? If the former hypothesis is correct, then the axiom, "_ex
nihilo nihil fit_," is false, even in relation to the ordinary course of
nature, seeing that such mutations of matter as imply the continual origin
of new substantial forms are occurring every moment. But the harmonisation
of Aristotle with theology was as dear to the Schoolmen, as the smoothing
down the differences between Moses and science is to our Broad Churchmen,
and they were proportionably unwilling to contradict one of Aristotle's
fundamental propositions. Nor was their objection to flying in the face of
the Stagirite likely to be lessened by the fact that such flight landed
them in flat Pantheism.
So Father Suarez fights stoutly for the second hypothesis; and I quote the
principal part of his argumentation as an exquisite specimen of that speech
which is a "darkening of counsel."
"13. Secundo de omnibus aliis formis substantialibus [sc. materialibus]
dicendum est non fieri proprie ex nihilo, sed ex potentia præjacentis
materiæ educi: ideoque in effectione harum formarum nil fieri contra illud
axioma, _Ex nihilo nihil fit_, si recte intelligatur. Hæc assertio
sumitur ex Aristotele 1. Physicorum per totum et libro 7. Metaphyss. et ex
aliis auctoribus, quos statim referam. Et declaratur breviter, nam fieri ex
nihilo duo dicit, unum est fieri absolute et simpliciter, aliud est quod
talis effectio fit ex nihilo. Primum propriè dicitur de re subsistente,
quia ejus est fieri, cujus est esse: id autem proprie quod subsistit et
habet esse; nam quod alteri adjacet, potius est quo aliud est. Ex hac ergo
parte, formæ substantiales materiales non fiunt ex nihilo, quia proprie non
fiunt. Atque hanc rationem reddit Divus Thomas 1 parte, quæstione 45,
articulo 8, et quæstione 90, articulo 2, et ex dicendis magis explicabitur.
Sumendo ergo ipsum _fieri_ in hac proprietate et rigore, sic fieri ex
nihilo est fieri secundum se totum, id est nulla sui parte præsupposita, ex
quo fiat. Et hac ratione res naturales dum de novo fiunt, non fiunt ex
nihilo, quia fiunt ex præsupposita materia, ex qua componuntur, et ita non
fiunt, secundum se totæ, sed secundum aliquid sui. Formæ autem harum rerum,
quamvis revera totam suam entitatem de novo accipiant, quam antea non
habebant, quia vero ipsæ non fiunt, ut dictum est, ideo neque ex nihilo
fiunt. Attamen, quia latiori modo sumendo verbum illud _fieri_ negari
non potest: quin forma facta sit, eo modo quo nunc est, et antea non erat,
ut etiam probat ratio dubitandi posita in principio sectionis, ideo
addendum est, sumpto _fieri_ in hac amplitudine, fieri ex nihilo non
tamen negare habitudinem materialis causæ intrinsecè componentis id quod
fit, sed etiam habitudinem causæ materialis per se causantis et
sustentantis formam quæ fit, seu confit. Diximus enim in superioribus
materiam et esse causam compositi et formæ dependentis ab illa: ut res ergo
dicatur ex nihilo fieri uterque modus causalitatis negari debet; et eodem
sensu accipiendum est illud axioma, ut sit verum: _Ex nihilo nihil
fit_, scilicet virtute agentis naturalis et finiti nihil fieri, nisi ex
præsupposito subjecto per se concurrente, et ad compositum et ad formam, si
utrumque suo modo ab eodem agente fiat. Ex his ergo rectè concluditur,
formas substantiales materiales non fieri ex nihilo, quia fiunt ex materia,
quæ in suo genere per se concurrit, et influit ad esse, et fieri talium
formarum; quia, sicut esse non possunt nisi affixae materiæ, a qua
sustententur in esse: ita nec fieri possunt, nisi earum effectio et
penetratio in eadem materia sustentetur. Et hæc est propria et per se
differentia inter effectionem ex nihilo, et ex aliquo, propter quam, ut
infra ostendemus, prior modus efficiendi superat vim finitam naturaliam
agentium, non vero posterior.
"14. Ex his etiam constat, proprie de his formis dici non creari, sed educi
de potentia materiæ." [Footnote: Suarez, _loc. cit._ Disput. xv. §
ii.]
If I may venture to interpret these hard sayings, Suarez conceives that the
evolution of substantial forms in the ordinary course of nature, is
conditioned not only by the existence of the _materia prima_, but also
by a certain "concurrence and influence" which that _materia_ exerts;
and every new substantial form being thus conditioned, and in part, at any
rate, caused, by a pre-existing something, cannot be said to be created out
of nothing.
But as the whole tenor of the context shows, Suarez applies this
argumentation merely to the evolution of material substantial forms in the
ordinary course of nature. How the substantial forms of animals and plants
primarily originated, is a question to which, so far as I am able to
discover, he does not so much as allude in his "Metaphysical Disputations."
Nor was there any necessity that he should do so, inasmuch as he has
devoted a separate treatise of considerable bulk to the discussion of all
the problems which arise out of the account of the Creation which is given
in the Book of Genesis. And it is a matter of wonderment to me that Mr.
Mivart, who somewhat sharply reproves "Mr. Darwin and others" for not
acquainting themselves with the true teachings of his Church, should allow
himself to be indebted to a heretic like myself for a knowledge of the
existence of that "Tractatus de opere sex Dierum," [Footnote: _Tractatus
de opere sex Dierum, seu de Universi Creatione, quatenus sex diebus
perfecta esse, in libro Genesis cap. i. refertur, et praesertim de
productione hominis in statu innocentiae._ Ed. Birckmann, 1622.] in
which the learned Father, of whom he justly speaks, as "an authority widely
venerated, and whose orthodoxy has never been questioned," directly opposes
all those opinions for which Mr. Mivart claims the shelter of his
authority.
In the tenth and eleventh chapters of the first book of this treatise,
Suarez inquires in what sense the word "day," as employed in the first
chapter of Genesis, is to be taken. He discusses the views of Philo and of
Augustin on this question, and rejects them. He suggests that the approval
of their allegorising interpretations by St. Thomas Aquinas, merely arose
out of St. Thomas's modesty, and his desire not to seem openly to
controvert St. Augustin--"voluisse Divus Thomas pro sua modestia
subterfugere vim argumenti potius quam aperte Augustinum inconstantiæ
arguere."
Finally, Suarez decides that the writer of Genesis meant that the term
"day" should be taken in its natural sense; and he winds up the discussion
with the very just and natural remark that "it is not probable that God, in
inspiring Moses to write a history of the Creation which was to be believed
by ordinary people, would have made him use language, the true meaning of
which it is hard to discover, and still harder to believe." [Footnote:
"Propter hæc ergo sententia illa Augustini et propter nimiam obscuritatem
et subtilitatem ejus difficilis creditu est: quia verisimile non est Deum
inspirasse Moysi, ut historiam de creatione mundi ad fidem totius populi
adeo necessariam per nomina dierum explicaret, quorum significatio vix
inveniri et difficillime ab aliquo credi posset." (_Loc. cit._ Lib. I.
cap. xi. 42.)]
And in chapter xii. 3, Suarez further observes:--
"Ratio enim retinendi veram significationem diei naturalis est illa
communis, quod verba Scripturæ non sunt ad metaphoras transferenda, nisi
vel necessitas cogit, vel ex ipsa scriptura constet, et maximè in historica
narratione et ad instructionem fidei pertinente: sed hæc ratio non minus
cogit ad intelligendum propriè dierum numerum, quam diei qualitatem, QUIA
NON MINUS UNO MODO QUAM ALIO DESTRUITUR SINCERITAS, IMO ET VERITAS
HISTORIÆ. Secundo hoc valde confirmant alia Scripturæ loca, in quibus hi
sex dies tanquam veri, et inter se distincti commemorantur, ut Exod. 20
dicitur, _Sex diebus operabis et facies omnia opera tua, septimo autem
die Sabbatum Domini Dei tui est_. Et infra: _Sex enim diebus fecit
Dominus cælum et terram et mare et omnia quæ in eis sunt_, et idem
repetitur in cap. 31. In quibus locis sermonis proprietas colligi potest
tum ex æquiparatione, nam cum dicitur: _sex diebus operabis_,
propriissimè intelligitur: tum quia non est verisimile, potuisse populum
intelligere verba illa in alio sensu, et è contrario incredibile est, Deum
in suis præceptis tradendis illis verbis ad populum fuisse loquutum, quibus
deciperetur, falsum sensum concipiendo, si Deus non per sex veros dies
opera sua fecisset."
These passages leave no doubt that this great doctor of the Catholic
Church, of unchallenged authority and unspotted orthodoxy, not only
declares it to be Catholic doctrine that the work of creation took place in
the space of six natural days; but that he warmly repudiates, as
inconsistent with our knowledge of the Divine attributes, the supposition
that the language which Catholic faith requires the believer to hold that
God inspired, was used in any other sense than that which He knew it would
convey to the minds of those to whom it was addressed.
And I think that in this repudiation Father Suarez will have the sympathy
of every man of common uprightness, to whom it is certainly "incredible"
that the Almighty should have acted in a manner which He would esteem
dishonest and base in a man.
But the belief that the universe was created in six natural days is
hopelessly inconsistent with the doctrine of evolution, in so far as it
applies to the stars and planetary bodies; and it can be made to agree with
a belief in the evolution of living beings only by the supposition that the
plants and animals, which are said to have been created on the third,
fifth, and sixth days, were merely the primordial forms, or rudiments, out
of which existing plants and animals have been evolved; so that, on these
days, plants and animals were not created actually, but only potentially.
The latter view is that held by Mr. Mivart, who follows St. Augustin, and
implies that he has the sanction of Suarez. But, in point of fact, the
latter great light of orthodoxy takes no small pains to give the most
explicit and direct contradiction to all such imaginations, as the
following passages prove. In the first place, as regards plants, Suarez
discusses the problem:--
"_Quomodo herba virens et cætera vegetabilia hoc_
[_tertio_] _die fuerint producta_.
[Footnote: _Loc. cit._ Lib. II. cap. vii. et viii. 1, 32, 35.]
"Præcipua enim difficultas hîc est, quam attingit Div. Thomas 1, par. qu.
69, art. 2, an hæc productio plantarum hoc die facta intelligenda sit de
productione ipsarum in proprio esse actuali et formali (ut sic rem
explicerem) vel de productione tantum in semine et in potentia. Nam Divus
Augustinus libro quinto Genes, ad liter. cap. 4 et 5 et libro 8, cap. 3,
posteriorem partem tradit, dicens, terram in hoc die accepisse virtutem
germinandi omnia vegetabilia quasi concepto omnium illorum semine, non
tamen statim vegetabilia omnia produxisse. Quod primo suadet verbis illis
capitis secundi. _In die quo fecit Deus cælum et terram et omne virgultum
agri priusquam germinaret_. Quomodo enim potuerunt virgulta fieri
antequam terra germinaret nisi quia causaliter prius et quasi in radice,
seu in semine facta sunt, et postea in actu producta? Secundo confirmari
potest, quia verbum illud _germinet terra_ optimè exponitur
potestativè ut sic dicam, id est accipiat terra vim germinandi. Sicut in
eodem capite dicitur _crescite et multiplicamini_. Tertio potest
confirmari, quia actualis productio vegetabilium non tam ad opus
creationis, quam ad opus propagationis pertinet, quod postea factum est. Et
hanc sententiam sequitur Eucherius lib. 1, in Gen. cap. 11, et illi faveat
Glossa, interli. Hugo. et Lyran. dum verbum _germinet_ dicto modo
exponunt. NIHILOMINUS CONTRARIA SENTENTIA TENENDA EST: SCILICET, PRODUXISSE
DEUM HOC DIE HERBAM, ARBORES, ET ALIA VEGETABILIA ACTU IN PROPRIA SPECIE ET
NATURA. Hæc est communis sententia Patrum.--Basil. homil. 5; Exæmer.
Ambros. lib. 3; Exæmer. cap. 8, 11, et 16; Chrysost. homil. 5 in Gen.
Damascene. lib. 2 de Fid. cap. 10; Theodor. Cyrilli. Bedæ, Glossæ ordinariæ
et aliorum in Gen. Et idem sentit Divus Thomas, _supra_, solvens
argumenta Augustini, quamvis propter reverentiam ejus quasi problematicè
semper procedat. Denique idem sentiunt omnes qui in his operibus veram
successionem et temporalem distinctionem agnoscant."
Secondly, with respect to animals, Suarez is no less decided:--
"_De animalium ratione carentium productione quinto et sexto die
facta_. [Footnote: _Loc. cit_. Lib. II. cap. vii. et viii. 1, 32,
35.]
"32. Primo ergo nobis certum sit hæc animantia non in virtute tantum aut in
semine, sed actu, et in seipsis, facta fuisse his diebus in quibus facta
narrantur. Quanquam Augustinus lib. 3, Gen. ad liter, cap. 5 in sua
persistens sententia contrarium sentire videatur."
But Suarez proceeds to refute Augustin's opinions at great length, and his
final judgment may be gathered from the following passage:--
"35. Tertio dicendum est, hæc animalia omnia his diebus producta esse, IN
PERFECTO STATU, IN SINGULIS INDIVIDUIS, SEU SPECIEBUS SUIS, JUXTA
UNIUSCUJUSQUE NATURAM.... ITAQUE FUERUNT OMNIA CREATA INTEGRA ET OMNIBUS
SUIS MEMBRIS PERFECTA."
As regards the creation of animals and plants, therefore, it is clear that
Suarez, so far from "distinctly asserting derivative creating," denies it
as distinctly and positively as he can; that he is at much pains to refute
St. Augustin's opinions; that he does not hesitate to regard the faint
acquiescence of St. Thomas Aquinas in the views of his brother saint as a
kindly subterfuge on the part of Divus Thomas; and that he affirms his own
view to be that which is supported by the authority of the Fathers of the
Church. So that, when Mr. Mivart tells us that Catholic theology is in
harmony with all that modern science can possibly require; that "to the
general theory of evolution, and to the special Darwinian form of it, no
exception ... need be taken on the ground of orthodoxy;" and that "law and
regularity, not arbitrary intervention, was the Patristic ideal of
creation," we have to choose between his dictum, as a theologian, and that
of a great light of his Church, whom he himself declares to be "widely
venerated as an authority, and whose orthodoxy has never been questioned."
But Mr. Mivart does not hesitate to push his attempt to harmonise science
with Catholic orthodoxy to its utmost limit; and, while assuming that the
soul of man "arises from immediate and direct creation," he supposes that
his body was "formed at first (as now in each separate individual) by
derivative, or secondary creation, through natural laws" (p. 331).
This means, I presume, that an animal, having the corporeal form and bodily
powers of man, may have been developed out of some lower form of life by a
process of evolution; and that, after this anthropoid animal had existed
for a longer or shorter time, God made a soul by direct creation, and put
it into the manlike body, which, heretofore, had been devoid of that
_anima rationalis_, which is supposed to be man's distinctive
character.
This hypothesis is incapable of either proof or disproof, and therefore may
be true; but if Suarez is any authority, it is not Catholic doctrine.
"Nulla est in homine forma educta de potentia materiæ," [Footnote: Disput.
xv. § x. No. 27.] is a dictum which is absolutely inconsistent with the
doctrine of the natural evolution of any vital manifestation of the human
body.
Moreover, if man existed as an animal before he was provided with a
rational soul, he must, in accordance with the elementary requirements of
the philosophy in which Mr. Mivart delights, have possessed a distinct
sensitive and vegetative soul, or souls. Hence, when the "breath of life"
was breathed into the manlike animal's nostrils, he must have already been
a living and feeling creature. But Suarez particularly discusses this
point, and not only rejects Mr. Mivart's view, but adopts language of very
theological strength regarding it.
"Possent præterea his adjungi argumenta theologica, ut est illud quod
sumitur ex illis verbis Genes. 2. _Formavit Deus hominem ex limo terræ et
inspiravit in faciem ejus spiraculum vitæ et factus est homo in animam
viventem_: ille enim spiritus, quam Deus spiravit, anima rationalis
fuit, et PER EADEM FACTUS EST HOMO VIVENS, ET CONSQUENTER, ETIAM SENTIENS.
"Aliud est ex VIII. Synodo Generali quæ est Constantinopolitana IV. can.
11, qui sic habet. _Apparet quosdam in tantum impietatis venisse ut
homines duas animas habere dogmatizent: talis igitur impietatis inventores
et similes sapientes, cum Vetus et Novum Testamentum omnesque Ecclesiæ
patres unam animam rationalem hominem habere asseverent, Sancta et
universalis Synodus anathematizat_." [FOOTNOTE: Disput. xv. "De causa
formali substantiali," § x. No. 24.]
Moreover, if the animal nature of man was the result of evolution, so must
that of woman have been. But the Catholic doctrine, according to Suarez, is
that woman was, in the strictest and most literal sense of the words, made
out of the rib of man.
"Nihilominus sententia Catholica est, verba illa Scripturæ esse ad literam
intelligenda. AC PROINDE VERE, AC REALITER, TULISSE DEUM COSTAM ADAMÆ, ET,
EX ILLA, CORPUS EVÆ FORMASSE." [Footnote: _Tractatus de Opere_, Lib.
III. "De hominis creatione," cap. ii. No. 3.]
Nor is there any escape in the supposition that some woman existed before
Eve, after the fashion of the Lilith of the rabbis; since Suarez qualifies
that notion, along with some other Judaic imaginations, as simply
"damnabilis." [Footnote: _Ibid_. Lib. III. cap. iv. Nos. 8 and 9]
After the perusal of the "Tractatus de Opere" it is, in fact, impossible to
admit that Suarez held any opinion respecting the origin of species, except
such as is consistent with the strictest and most literal interpretation of
the words of Genesis. For Suarez, it is Catholic doctrine, that the world
was made in six natural days. On the first of these days the _materia
prima_ was made out of nothing, to receive afterwards those "substantial
forms" which moulded it into the universe of things; on the third day, the
ancestors of all living plants suddenly came into being, full-grown,
perfect, and possessed of all the properties which now distinguish them;
while, on the fifth and sixth days, the ancestors of all existing animals
were similarly caused to exist in their complete and perfect state, by the
infusion of their appropriate material substantial forms into the matter
which had already been created. Finally, on the sixth day, the _anima
rationalis_--that rational and immortal substantial form which is
peculiar to man--was created out of nothing, and "breathed into" a mass of
matter which, till then, was mere dust of the earth, and so man arose. But
the species man was represented by a solitary male individual, until the
Creator took out one of his ribs and fashioned it into a female.
This is the view of the "Genesis of Species" held by Suarez to be the only
one consistent with Catholic faith: it is because he holds this view to be
Catholic that he does not hesitate to declare St. Augustin unsound, and St.
Thomas Aquinas guilty of weakness, when the one swerved from this view and
the other tolerated the deviation. And, until responsible Catholic
authority--say, for example, the Archbishop of Westminster--formally
declares that Suarez was wrong, and that Catholic priests are free to teach
their flocks that the world was _not_ made in six natural days, and
that plants and animals were _not_ created in their perfect and
complete state, but have been evolved by natural processes through long
ages from certain germs in which they were potentially contained, I, for
one, shall feel bound to believe that the doctrines of Suarez are the only
ones which are sanctioned by Infallible Authority, as represented by the
Holy Father and the Catholic Church.
I need hardly add that they are as absolutely denied and repudiated by
Scientific Authority, as represented by Reason and Fact. The question
whether the earth and the immediate progenitors of its present living
population were made in six natural days or not is no longer one upon which
two opinions can be held.
The fact that it did not so come into being stands upon as sound a basis as
any fact of history whatever. It is not true that existing plants and
animals came into being within three days of the creation of the earth out
of nothing, for it is certain that innumerable generations of other plants
and animals lived upon the earth before its present population. And when,
Sunday after Sunday, men who profess to be our instructors in righteousness
read out the statement, "In six days the Lord made heaven and earth, the
sea, and all that in them is," in innumerable churches, they are either
propagating what they may easily know, and, therefore, are bound to know,
to be falsities; or, if they use the words in some non-natural sense, they
fall below the moral standard of the much-abused Jesuit.
Thus far the contradiction between Catholic verity and Scientific verity is
complete and absolute, quite independently of the truth or falsehood of the
doctrine of evolution. But, for those who hold the doctrine of evolution,
all the Catholic verities about the creation of living beings must be no
less false. For them, the assertion that the progenitors of all existing
plants were made on the third day, of animals on the fifth and sixth days,
in the forms they now present, is simply false. Nor can they admit that man
was made suddenly out of the dust of the earth; while it would be an insult
to ask an evolutionist whether he credits the preposterous fable respecting
the fabrication of woman to which Suarez pins his faith. If Suarez has
rightly stated Catholic doctrine, then is evolution utter heresy. And such
I believe it to be. In addition to the truth of the doctrine of evolution,
indeed, one of its greatest merits in my eyes, is the fact that it occupies
a position of complete and irreconcilable antagonism to that vigorous and
consistent enemy of the highest intellectual, moral, and social life of
mankind--the Catholic Church. No doubt, Mr. Mivart, like other putters of
new wine into old bottles, is actuated by motives which are worthy of
respect, and even of sympathy; but his attempt has met with the fate which
the Scripture prophesies for all such.
Catholic theology, like all theologies which are based upon the assumption
of the truth of the account of the origin of things given in the Book of
Genesis, being utterly irreconcilable with the doctrine of evolution, the
student of science, who is satisfied that the evidence upon which the
doctrine of evolution rests, is incomparably stronger and better than that
upon which the supposed authority of the Book of Genesis rests, will not
trouble himself further with these theologies, but will confine his
attention to such arguments against the view he holds as are based upon
purely scientific data--and by scientific data I do not merely mean the
truths of physical, mathematical, or logical science, but those of moral
and metaphysical science. For by science I understand all knowledge which
rests upon evidence and reasoning of a like character to that which claims
our assent to ordinary scientific propositions. And if any one is able to
make good the assertion that his theology rests upon valid evidence and
sound reasoning, then it appears to me that such theology will take its
place as a part of science.
The present antagonism between theology and science does not arise from any
assumption by the men of science that all theology must necessarily be
excluded from science, but simply because they are unable to allow that
reason and morality have two weights and two measures; and that the belief
in a proposition, because authority tells you it is true, or because you
wish to believe it, which is a high crime and misdemeanour when the subject
matter of reasoning is of one kind, becomes under the _alias_ of
"faith" the greatest of all virtues when the subject matter of reasoning is
of another kind.
The Bishop of Brechin said well the other day:--"Liberality in religion--I
do not mean tender and generous allowances for the mistakes of others--is
only unfaithfulness to truth." [Footnote: Charge at the Diocesan Synod of
Brechin. _Scotsman_, Sept. 14, 1871.] And, with the same
qualification, I venture to paraphrase the Bishop's dictum:
"Ecclesiasticism in science is only unfaithfulness to truth."
Elijah's great question, "Will you serve God or Baal? Choose ye," is
uttered audibly enough in the ears of every one of us as we come to
manhood. Let every man who tries to answer it seriously ask himself whether
he can be satisfied with the Baal of authority, and with all the good
things his worshippers are promised in this world and the next. If he can,
let him, if he be so inclined, amuse himself with such scientific
implements as authority tells him are safe and will not cut his fingers;
but let him not imagine he is, or can be, both a true son of the Church and
a loyal soldier of science.
And, on the other hand, if the blind acceptance of authority appears to him
in its true colours, as mere private judgment _in excelsis_, and if he
have the courage to stand alone, face to face with the abyss of the eternal
and unknowable, let him be content, once for all, not only to renounce the
good things promised by "Infallibility," but even to bear the bad things
which it prophesies; content to follow reason and fact in singleness and
honesty of purpose, wherever they may lead, in the sure faith that a hell
of honest men will, to him, be more endurable than a paradise full of
angelic shams.
Mr. Mivart asserts that "without a belief in a personal God there is no
religion worthy of the name." This is a matter of opinion. But it may be
asserted, with less reason to fear contradiction, that the worship of a
personal God, who, on Mr. Mivart's hypothesis, must have used language
studiously calculated to deceive His creatures and worshippers, is "no
religion worthy of the name." "Incredible est, Deum illis verbis ad populum
fuisse locutum quibus deciperetur," is a verdict in which, for once, Jesuit
casuistry concurs with the healthy moral sense of all mankind.
Having happily got quit of the theological aspect of evolution, the
supporter of that great truth who turns to the scientific objections which
are brought against it by recent criticism, finds, to his relief, that the
work before him is greatly lightened by the spontaneous retreat of the
enemy from nine-tenths of the territory which he occupied ten years ago.
Even the Quarterly Reviewer not only abstains from venturing to deny that
evolution has taken place, but he openly admits that Mr. Darwin has forced
on men's minds "a recognition of the probability, if not more, of
evolution, and of the certainty of the action of natural selection" (p.
49).
I do not quite see, myself, how, if the action of natural selection is
_certain_, the occurrence of evolution is only _probable_;
inasmuch as the development of a new species by natural selection is, so
far as it goes, evolution. However, it is not worth while to quarrel with
the precise terms of a sentence which shows that the high water mark of
intelligence among those most respectable of Britons, the readers of the
_Quarterly Review_, has now reached such a level that the next tide
may lift them easily and pleasantly on the once-dreaded shore of evolution.
Nor, having got there, do they seem likely to stop, until they have reached
the inmost heart of that great region, and accepted the ape ancestry of, at
any rate, the body of man. For the Reviewer admits that Mr. Darwin can be
said to have established:
"That if the various kinds of lower animals have been evolved one from the
other by a process of natural generation or evolution, then it becomes
highly probable, _a priori_, that man's body has been similarly
evolved; but this, in such a case, becomes equally probable from the
admitted fact that he is an animal at all" (p. 65).
From the principles laid down in the last sentence it would follow that if
man were constructed upon a plan as different from that of any other animal
as that of a sea-urchin is from that of a whale, it would be "equally
probable" that he had been developed from some other animal as it is now,
when we know that for every bone, muscle, tooth, and even pattern of tooth,
in man, there is a corresponding bone, muscle, tooth, and pattern of tooth,
in an ape. And this shows one of two things--either that the Quarterly
Reviewer's notions of probability are peculiar to himself, or that he has
such an overpowering faith in the truth of evolution that no extent of
structural break between one animal and another is sufficient to destroy
his conviction that evolution has taken place.
But this by the way. The importance of the admission that there is nothing
in man's physical structure to interfere with his having been evolved from
an ape is not lessened because it is grudgingly made and inconsistently
qualified. And instead of jubilating over the extent of the enemy's
retreat, it will be more worth while to lay siege to his last
stronghold--the position that there is a distinction in kind between the
mental faculties of man and those of brutes, and that in consequence of
this distinction in kind no gradual progress from the mental faculties of
the one to those of the other can have taken place.
The Quarterly Reviewer entrenches himself within formidable-looking
psychological outworks, and there is no getting at him without attacking
them one by one.
He begins by laying down the following proposition. "'Sensation' is not
'thought,' and no amount of the former would constitute the most
rudimentary condition of the latter, though sensations supply the
conditions for the existence of 'thought' or 'knowledge'" (p. 67).
This proposition is true, or not, according to the sense in which the word
"thought" is employed. Thought is not uncommonly used in a sense
co-extensive with consciousness, and, especially, with those states of
consciousness we call memory. If I recall the impression made by a colour
or an odour, and distinctly remember blueness or muskiness, I may say with
perfect propriety that I "think of" blue or musk; and, so long as the
thought lasts, it is simply a faint reproduction of the state of
consciousness to which I gave the name in question, when it first became
known to me as a sensation.
Now, if that faint reproduction of a sensation, which we call the memory of
it, is properly termed a thought, it seems to me to be a somewhat forced
proceeding to draw a hard and fast line of demarcation between thoughts and
sensations. If sensations are not rudimentary thoughts, it may be said that
some thoughts are rudimentary sensations. No amount of sound constitutes an
echo, but for all that no one would pretend that an echo is something of
totally different nature from a sound. Again, nothing can be looser, or
more inaccurate, than the assertion that "sensations supply the conditions
for the existence of thought or knowledge." If this implies that sensations
supply the conditions for the existence of our memory of sensations or of
our thoughts about sensations, it is a truism which it is hardly worth
while to state so solemnly. If it implies that sensations supply anything
else, it is obviously erroneous. And if it means, as the context would seem
to show it does, that sensations are the subject-matter of all thought or
knowledge, then it is no less contrary to fact, inasmuch as our emotions,
which constitute a large part of the subject-matter of thought or of
knowledge, are not sensations.
More eccentric still is the Quarterly Reviewer's next piece of psychology.
"Altogether, we may clearly distinguish at least six kinds of action to
which the nervous system ministers:--
"I. That in which impressions received result in appropriate movements
without the intervention of sensation or thought, as in the cases of injury
above given.--This is the reflex action of the nervous system.
"II. That in which stimuli from without result in sensations through the
agency of which their due effects are wrought out.--Sensation.
"III. That in which impressions received result in sensations which give
rise to the observation of sensible objects.--Sensible perception.
"IV. That in which sensations and perceptions continue to coalesce,
agglutinate, and combine in more or less complex aggregations, according to
the laws of the association of sensible perceptions.--Association.
"The above four groups contain only indeliberate operations, consisting, as
they do at the best, but of mere _presentative_ sensible ideas in no
way implying any reflective or _representative_ faculty. Such actions
minister to and form _Instinct_. Besides these, we may distinguish two
other kinds of mental action, namely:--
"V. That in which sensations and sensible perceptions are reflected on by
thought, and recognised as our own, and we ourselves recognised by
ourselves as affected and perceiving.--Self-consciousness.
"VI. That in which we reflect upon our sensations or perceptions, and ask
what they are, and why they are.--Reason.
"These two latter kinds of action are deliberate operations, performed, as
they are, by means of representative ideas implying the use of a
_reflective representative_ faculty. Such actions distinguish the
_intellect_ or rational faculty. Now, we assert that possession in
perfection of all the first four (_presentative_) kinds of action by
no means implies the possession of the last two (_representative_)
kinds. All persons, we think, must admit the truth of the following
proposition:--
"Two faculties are distinct, not in degree but _in kind_, if we may
possess the one in perfection without that fact implying that we possess
the other also. Still more will this be the case if the two faculties tend
to increase in an inverse ratio. Yet this is the distinction between the
_instinctive_ and the _intellectual_ parts of man's nature.
"As to animals, we fully admit that they may possess all the first four
groups of actions--that they may have, so to speak, mental images of
sensible objects combined in all degrees of complexity, as governed by the
laws of association. We deny to them, on the other hand, the possession of
the last two kinds of mental action. We deny them, that is, the power of
reflecting on their own existences, or of inquiring into the nature of
objects and their causes. We deny that they know that they know or know
themselves in knowing. In other words, we deny them _reason_. The
possession of the presentative faculty, as above explained, in no way
implies that of the reflective faculty; nor does any amount of direct
operation imply the power of asking the reflective question before
mentioned, as to 'what' and 'why.'" (_Loc. cit_. pp. 67, 68.)
Sundry points are worthy of notice in this remarkable account of the
intellectual powers. In the first place the Reviewer ignores emotion and
volition, though they are no inconsiderable "kinds of action to which the
nervous system ministers," and memory has a place in his classification
only by implication. Secondly, we are told that the second "kind of action
to which the nervous system ministers" is "that in which stimuli from
without result in sensations through the agency of which their due effects
are wrought out.--Sensation." Does this really mean that, in the writer's
opinion, "sensation" is the "agent" by which the "due effect" of the
stimulus, which gives rise to sensation, is "wrought out"? Suppose somebody
runs a pin into me. The "due effect" of that particular stimulus will
probably be threefold; namely, a sensation of pain, a start, and an
interjectional expletive. Does the Quarterly Reviewer really think that the
"sensation" is the "agent" by which the other two phenomena are wrought
out?
But these matters are of little moment to anyone but the Reviewer and those
persons who may incautiously take their physiology, or psychology, from
him. The really interesting point is this, that when he fully admits that
animals "may possess all the first four groups of actions," he grants all
that is necessary for the purposes of the evolutionist. For he hereby
admits that in animals "impressions received result in sensations which
give rise to the observation of sensible objects," and that they have what
he calls "sensible perception." Nor was it possible to help the admission;
for we have as much reason to ascribe to animals, as we have to attribute
to our fellow-men, the power, not only of perceiving external objects as
external, and thus practically recognizing the difference between the self
and the not-self; but that of distinguishing between like and unlike, and
between simultaneous and successive things. When a gamekeeper goes out
coursing with a greyhound in leash, and a hare crosses the field of vision,
he becomes the subject of those states of consciousness we call visual
sensation, and that is all he receives from without. Sensation, as such,
tells him nothing whatever about the cause of these states of
consciousness; but the thinking faculty instantly goes to work upon the raw
material of sensation furnished to it through the eye, and gives rise to a
train of thoughts. First comes the thought that there is an object at a
certain distance; then arises another thought--the perception of the
likeness between the states of consciousness awakened by this object to
those presented by memory, as, on some former occasion, called up by a
hare; this is succeeded by another thought of the nature of an
emotion--namely, the desire to possess the hare; then follows a longer or
shorter train of other thoughts, which end in a volition and an act--the
loosing of the greyhound from the leash. These several thoughts are the
concomitants of a process which goes on in the nervous system of the man.
Unless the nerve-elements of the retina, of the optic nerve, of the brain,
of the spinal cord, and of the nerves of the arms, went through certain
physical changes in due order and correlation, the various states of
consciousness which have been enumerated would not make their appearance.
So that in this, as in all other intellectual operations, we have to
distinguish two sets of successive changes--one in the physical basis of
consciousness, and the other in consciousness itself; one set which may,
and doubtless will, in course of time, be followed through all their
complexities by the anatomist and the physicist, and one of which only the
man himself can have immediate knowledge.
As it is very necessary to keep up a clear distinction between these two
processes, let the one be called _neurosis_, and the other
_psychosis_. When the gamekeeper was first trained to his work every
step in the process of neurosis was accompanied by a corresponding step in
that of psychosis, or nearly so. He was conscious of seeing something,
conscious of making sure it was a hare, conscious of desiring to catch it,
and therefore to loose the greyhound at the right time, conscious of the
acts by which he let the dog out of the leash. But with practice, though
the various steps of the neurosis remain--for otherwise the impression on
the retina would not result in the loosing of the dog--the great majority
of the steps of the psychosis vanish, and the loosing of the dog follows
unconsciously, or as we say, without thinking about it, upon the sight of
the hare. No one will deny that the series of acts which originally
intervened between the sensation and the letting go of the dog were, in the
strictest sense, intellectual and rational operations. Do they cease to be
so when the man ceases to be conscious of them? That depends upon what is
the essence and what the accident of those operations, which, taken
together, constitute ratiocination.
Now ratiocination is resolvable into predication, and predication consists
in marking, in some way, the existence, the co-existence, the succession,
the likeness and unlikeness, of things or their ideas. Whatever does this,
reasons; and if a machine produces the effects of reason, I see no more
ground for denying to it the reasoning power, because it is unconscious,
than I see for refusing to Mr. Babbage's engine the title of a calculating
machine on the same grounds.
Thus it seems to me that a gamekeeper reasons, whether he is conscious or
unconscious, whether his reasoning is carried on by neurosis alone, or
whether it involves more or less psychosis. And if this is true of the
gamekeeper, it is also true of the greyhound. The essential resemblances in
all points of structure and function, so far as they can be studied,
between the nervous system of the man and that of the dog, leave no
reasonable doubt that the processes which go on in the one are just like
those which take place in the other. In the dog, there can be no doubt that
the nervous matter which lies between the retina and the muscles undergoes
a series of changes, precisely analogous to those which, in the man, give
rise to sensation, a train of thought, and volition.
Whether this neurosis is accompanied by such psychosis as ours it is
impossible to say; but those who deny that the nervous changes, which, in
the dog, correspond with those which underlie thought in a man, are
accompanied by consciousness, are equally bound to maintain that those
nervous changes in the dog, which correspond with those which underlie
sensation in a man, are also unaccompanied by consciousness. In other
words, if there is no ground for believing that a dog thinks, neither is
there any for believing that he feels.
As is well known, Descartes boldly faced this dilemma, and maintained that
all animals were mere machines and entirely devoid of consciousness. But he
did not deny, nor can anyone deny, that in this case they are reasoning
machines, capable of performing all those operations which are performed by
the nervous system of man when he reasons. For even supposing that in man,
and in man only, psychosis is superadded to neurosis--the neurosis which is
common to both man and animal gives their reasoning processes a fundamental
unity. But Descartes' position is open to very serious objections if the
evidence that animals feel is insufficient to prove that they really do so.
What is the value of the evidence which leads one to believe that one's
fellow-man feels? The only evidence in this argument of analogy is the
similarity of his structure and of his actions to one's own. And if that is
good enough to prove that one's fellow-man feels, surely it is good enough
to prove that an ape feels. For the differences of structure and function
between men and apes are utterly insufficient to warrant the assumption
that while men have those states of consciousness we call sensations apes
have nothing of the kind. Moreover, we have as good evidence that apes are
capable of emotion and volition as we have that men other than ourselves
are. But if apes possess three out of the four kinds of states of
consciousness which we discover in ourselves, what possible reason is there
for denying them the fourth? If they are capable of sensation, emotion, and
volition, why are they to be denied thought (in the sense of predication)?
No answer has ever been given to these questions. And as the law of
continuity is as much opposed, as is the common sense of mankind, to the
notion that all animals are unconscious machines, it may safely be assumed
that no sufficient answer ever will be given to them.
There is every reason to believe that consciousness is a function of
nervous matter, when that nervous matter has attained a certain degree of
organisation, just as we know the other "actions to which the nervous
system ministers," such as reflex action and the like, to be. As I have
ventured to state my view of the matter elsewhere, "our thoughts are the
expression of molecular changes in that matter of life which is the source
of our other vital phenomena."
Mr. Wallace objects to this statement in the following terms:--
"Not having been able to find any clue in Professor Huxley's writings to
the steps by which he passes from those vital phenomena, which consist
only, in their last analysis, of movements by particles of matter, to those
other phenomena which we term thought, sensation, or consciousness; but,
knowing that so positive an expression of opinion from him will have great
weight with many persons, I shall endeavour to show, with as much brevity
as is compatible with clearness, that this theory is not only incapable of
proof, but is also, as it appears to me, inconsistent with accurate
conceptions of molecular physics."
With all respect for Mr. Wallace, it appears to me that his remarks are
entirely beside the question. I really know nothing whatever, and never
hope to know anything, of the steps by which the passage from molecular
movement to states of consciousness is effected; and I entirely agree with
the sense of the passage which he quotes from Professor Tyndall, apparently
imagining that it is in opposition to the view I hold.
All that I have to say is, that, in my belief, consciousness and molecular
action are capable of being expressed by one another, just as heat and
mechanical action are capable of being expressed in terms of one another.
Whether we shall ever be able to express consciousness in foot-pounds, or
not, is more than I will venture to say; but that there is evidence of the
existence of some correlation between mechanical motion and consciousness,
is as plain as anything can be. Suppose the poles of an electric battery to
be connected by a platinum wire. A certain intensity of the current gives
rise in the mind of a bystander to that state of consciousness we call a
"dull red light"--a little greater intensity to another which we call a
"bright red light;" increase the intensity, and the light becomes white;
and, finally, it dazzles, and a new state of consciousness arises, which we
term pain. Given the same wire and the same nervous apparatus, and the
amount of electric force required to give rise to these several states of
consciousness will be the same, however often the experiment is repeated.
And as the electric force, the light waves, and the nerve-vibrations caused
by the impact of the light-waves on the retina, are all expressions of the
molecular changes which are taking place in the elements of the battery; so
consciousness is, in the same sense, an expression of the molecular changes
which take place in that nervous matter, which is the organ of
consciousness.
And, since this, and any number of similar examples that may be required,
prove that one form of consciousness, at any rate, is, in the strictest
sense, the expression of molecular change, it really is not worth while to
pursue the inquiry, whether a fact so easily established is consistent with
any particular system of molecular physics or not.
Mr. Wallace, in fact, appears to me to have mixed up two very distinct
propositions: the one, the indisputable truth that consciousness is
correlated with molecular changes in the organ of consciousness; the other,
that the nature of that correlation is known, or can be conceived, which is
quite another matter. Mr. Wallace, presumably, believes in that correlation
of phenomena which we call cause and effect as firmly as I do. But if he
has ever been able to form the faintest notion how a cause gives rise to
its effect, all I can say is that I envy him. Take the simplest case
imaginable--suppose a ball in motion to impinge upon another ball at rest.
I know very well, as a matter of fact, that the ball in motion will
communicate some of its motion to the ball at rest, and that the motion of
the two balls, after collision, is precisely correlated with the masses of
both balls and the amount of motion of the first. But how does this come
about? In what manner can we conceive that the _vis viva_ of the first
ball passes into the second? I confess I can no more form any conception of
what happens in this case, than I can of what takes place when the motion
of particles of my nervous matter, caused by the impact of a similar ball
gives rise to the state of consciousness I call pain. In ultimate analysis
everything is incomprehensible, and the whole object of science is simply
to reduce the fundamental incomprehensibilities to the smallest possible
number.
But to return to the Quarterly Reviewer. He admits that animals have
"mental images of sensible objects, combined in all degrees of complexity,
as governed by the laws of association." Presumably, by this confused and
imperfect statement the Reviewer means to admit more than the words imply.
For mental images of sensible objects, even though "combined in all degrees
of complexity," are, and can be, nothing more than mental images of
sensible objects. But judgments, emotions, and volitions cannot by any
possibility be included under the head of "mental images of sensible
objects." If the greyhound had no better mental endowment than the Reviewer
allows him, he might have the "mental image" of the "sensible object"--the
hare--and that might be combined with the mental images of other sensible
objects, to any degree of complexity, but he would have no power of judging
it to be at a certain distance from him; no power of perceiving its
similarity to his memory of a hare; and no desire to get at it.
Consequently he would stand stock still, and the noble art of coursing
would have no existence. On the other hand, as that art is largely
practised, it follows that greyhounds alone possess a number of mental
powers, the existence of which, in any animal, is absolutely denied by the
Quarterly Reviewer.
Finally, what are the mental powers which he reserves as the especial
prerogative of man? They are two. First, the recognition of "ourselves by
ourselves as affected and perceiving.--Self-consciousness."
Secondly. "The reflection upon our sensations and perceptions, and asking
what they are and why they are.--Reason."
To the faculty defined in the last sentence, the Reviewer, without
assigning the least ground for thus departing from both common usage and
technical propriety, applies the name of reason. But if man is not to be
considered a reasoning being, unless he asks what his sensations and
perceptions are, and why they are, what is a Hottentot, or an Australian
"black-fellow"; or what the "swinked hedger" of an ordinary agricultural
district? Nay, what becomes of an average country squire or parson? How
many of these worthy persons who, as their wont is, read the _Quarterly
Review_, would do other than stand agape, if you asked them whether they
had ever reflected what their sensations and perceptions are and why they
are?
So that if the Reviewer's new definition of reason be correct, the majority
of men, even among the most civilised nations, are devoid of that supreme
characteristic of manhood. And if it be as absurd as I believe it to be,
then, as reason is certainly not self-consciousness, and since it, as
certainly, is one of the "actions to which the nervous system ministers,"
we must, if the Reviewer's classification is to be adopted, seek it among
those four faculties which he allows animals to possess. And thus, for the
second time, he really surrenders, while seeming to defend, his position.
The Quarterly Reviewer, as we have seen, lectures the evolutionists upon
their want of knowledge of philosophy altogether. Mr. Mivart is not less
pained at Mr. Darwin's ignorance of moral science. It is grievous to him
that Mr. Darwin (and _nous autres_) should not have grasped the
elementary distinction between material and formal morality; and he lays
down as an axiom, of which no tyro ought to be ignorant, the position that
"acts, unaccompanied by mental acts of conscious will directed towards the
fulfilment of duty," are "absolutely destitute of the most incipient degree
of real or formal goodness."
Now this may be Mr. Mivart's opinion, but it is a proposition which really
does not stand on the footing of an undisputed axiom. Mr. Mill denies it in
his work on Utilitarianism. The most influential writer of a totally
opposed school, Mr. Carlyle, is never weary of denying it, and upholding
the merit of that virtue which is unconscious; nay, it is, to my
understanding, extremely hard to reconcile Mr. Mivart's dictum with that
noble summary of the whole duty of man--"Thou shalt love the Lord thy God
with all thy heart, and with all thy soul, and with all thy strength; and
thou shalt love thy neighbour as thyself." According to Mr. Mivart's
definition, the man who loves God and his neighbour, and, out of sheer love
and affection for both, does all he can to please them, is, nevertheless,
destitute of a particle of real goodness.
And it further happens that Mr. Darwin, who is charged by Mr. Mivart with
being ignorant of the distinction between material and formal goodness,
discusses the very question at issue in a passage which is well worth
reading (vol. i. p. 87), and also comes to a conclusion opposed to Mr.
Mivart's axiom. A proposition which has been so much disputed and
repudiated, should, under no circumstances, have been thus confidently
assumed to be true. For myself, I utterly reject it, inasmuch as the
logical consequence of the adoption of any such principle is the denial of
all moral value to sympathy and affection. According to Mr. Mivart's axiom,
the man who, seeing another struggling in the water, leaps in at the risk
of his own life to save him, does that which is "destitute of the most
incipient degree of real goodness," unless, as he strips off his coat, he
says to himself, "Now, mind, I am going to do this because it is my duty
and for no other reason;" and the most beautiful character to which
humanity can attain, that of the man who does good without thinking about
it, because he loves justice and mercy and is repelled by evil, has no
claim on our moral approbation. The denial that a man acts morally because
he does not think whether he does so or not, may be put upon the same
footing as the denial of the title of an arithmetician to the calculating
boy, because he did not know how he worked his sums. If mankind ever
generally accept and act upon Mr. Mivart's axiom, they will simply become a
set of most unendurable prigs; but they never have accepted it, and I
venture to hope that evolution has nothing so terrible in store for the
human race.
But if an action, the motive of which is nothing but affection or sympathy,
may be deserving of moral approbation and really good, who that has ever
had a dog of his own will deny that animals are capable of such actions?
Mr. Mivart indeed says:--"It may be safely affirmed, however, that there is
no trace in brutes of any actions simulating morality which are not
explicable by the fear of punishment, by the hope of pleasure, or by
personal affection" (p. 221). But it may be affirmed, with equal truth,
that there is no trace in men of any actions which are not traceable to the
same motives. If a man does anything, he does it either because he fears to
be punished if he does not do it, or because he hopes to obtain pleasure by
doing it, or because he gratifies his affections [Footnote: In separating
pleasure and the gratification of affection, I simply follow Mr. Mivart
without admitting the justice of the separation.] by doing it.
Assuming the position of the absolute moralists, let it be granted that
there is a perception of right and wrong innate in every man. This means,
simply, that when certain ideas are presented to his mind, the feeling of
approbation arises; and when certain others, the feeling of disapprobation.
To do your duty is to earn the approbation of your conscience, or moral
sense; to fail in your duty is to feel its disapprobation, as we all say.
Now, is approbation a pleasure or a pain? Surely a pleasure. And is
disapprobation a pleasure or a pain? Surely a pain. Consequently, all that
is really meant by the absolute moralists is that there is, in the very
nature of man, something which enables him to be conscious of these
particular pleasures and pains. And when they talk of immutable and eternal
principles of morality, the only intelligible sense which I can put upon
the words, is that the nature of man being what it is, he always has been,
and always will be, capable of feeling these particular pleasures and
pains. _À priori,_ I have nothing to say against this proposition.
Admitting its truth, I do not see how the moral faculty is on a different
footing from any of the other faculties of man. If I choose to say that it
is an immutable and eternal law of human nature that "ginger is hot in the
mouth," the assertion has as much foundation of truth as the other, though
I think it would be expressed in needlessly pompous language. I must
confess that I have never been able to understand why there should be such
a bitter quarrel between the intuitionists and the utilitarians. The
intuitionist is, after all, only a utilitarian who believes that a
particular class of pleasures and pains has an especial importance, by
reason of its foundation in the nature of man, and its inseparable
connection with his very existence as a thinking being. And as regards the
motive of personal affection: Love, as Spinoza profoundly says, is the
association of pleasure with that which is loved. [Footnote: "Nempe, Amor
nihil aliud est, quam Lætitia, concomitante idea causæ
externæ."--_Ethices_, III. xiii.] Or, to put it to the common sense of
mankind, is the gratification of affection a pleasure or a pain? Surely a
pleasure. So that whether the motive which leads us to perform an action is
the love of our neighbour, or the love of God, it is undeniable that
pleasure enters into that motive.
Thus much in reply to Mr. Mivart's arguments. I cannot but think that it is
to be regretted that he ekes them out by ascribing to the doctrines of the
philosophers with whom he does not agree, logical consequences which have
been over and over again proved not to flow from them: and when reason
fails him, tries the effect of an injurious nickname. According to the
views of Mr. Spencer, Mr. Mill, and Mr. Darwin, Mr. Mivart tells us,
"_virtue is a mere kind of retrieving:_" and, that we may not miss the
point of the joke, he puts it in italics. But what if it is? Does that make
it less virtue? Suppose I say that sculpture is a "mere way" of
stone-cutting, and painting a "mere way" of daubing canvas, and music a
"mere way" of making a noise, the statements are quite true; but they only
show that I see no other method of depreciating some of the noblest aspects
of humanity than that of using language in an inadequate and misleading
sense about them. And the peculiar inappropriateness of this particular
nickname to the views in question, arises from the circumstance which Mr.
Mivart would doubtless have recollected, if his wish to ridicule had not
for the moment obscured his judgment--that whether the law of evolution
applies to man or not, that of hereditary transmission certainly does. Mr.
Mivart will hardly deny that a man owes a large share of the moral
tendencies which he exhibits to his ancestors; and the man who inherits a
desire to steal from a kleptomaniac, or a tendency to benevolence from a
Howard, is, so far as he illustrates hereditary transmission, comparable to
the dog who inherits the desire to fetch a duck out of the water from his
retrieving sire. So that, evolution, or no evolution, moral qualities are
comparable to a "kind of retrieving;" though the comparison, if meant for
the purposes of casting obloquy on evolution, does not say much for the
fairness of those who make it.
The Quarterly Reviewer and Mr. Mivart base their objections to the
evolution of the mental faculties of man from those of some lower animal
form upon what they maintain to be a difference in kind between the mental
and moral faculties of men and brutes; and I have endeavoured to show, by
exposing the utter unsoundness of their philosophical basis, that these
objections are devoid of importance.
The objections which Mr. Wallace brings forward to the doctrine of the
evolution of the mental faculties of man from those of brutes by natural
causes, are of a different order, and require separate consideration.
If I understand him rightly, he by no means doubts that both the bodily and
the mental faculties of man have been evolved from those of some lower
animal; but he is of opinion that some agency beyond that which has been
concerned in the evolution of ordinary animals has been operative in the
case of man. "A superior intelligence has guided the development of man in
a definite direction and for a special purpose, just as man guides the
development of many animal and vegetable forms." [Footnote: "The Limits of
Natural Selection as applied to Man" (_loc. cit._ p. 359).] I
understand this to mean that, just as the rock-pigeon has been produced by
natural causes, while the evolution of the tumbler from the blue rock has
required the special intervention of the intelligence of man, so some
anthropoid form may have been evolved by variation and natural selection;
but it could never have given rise to man, unless some superior
intelligence had played the part of the pigeon-fancier.
According to Mr. Wallace, "whether we compare the savage with the higher
developments of man, or with the brutes around him, we are alike driven to
the conclusion, that, in his large and well-developed brain, he possesses
an organ quite disproportioned to his requirements" (p. 343); and he asks,
"What is there in the life of the savage but the satisfying of the cravings
of appetite in the simplest and easiest way? What thoughts, idea, or
actions are there that raise him many grades above the elephant or the
ape?" (p. 342.) I answer Mr. Wallace by citing a remarkable passage which
occurs in his instructive paper on "Instinct in Man and Animals."
"Savages make long journeys in many directions, and, their whole faculties
being directed to the subject, they gain a wide and accurate knowledge of
the topography, not only of their own district, but of all the regions
round about. Every one who has travelled in a new direction communicates
his knowledge to those who have travelled less, and descriptions of routes
and localities, and minute incidents of travel, form one of the main
staples of conversation around the evening fire. Every wanderer or captive
from another tribe adds to the store of information, and, as the very
existence of individuals and of whole families and tribes depends upon the
completeness of this knowledge, all the acute perceptive faculties of the
adult savage are directed to acquiring and perfecting it. The good hunter
or warrior thus comes to know the bearing of every hill and mountain range,
the directions and junctions of all the streams, the situation of each
tract characterised by peculiar vegetation, not only within the area he has
himself traversed, but perhaps for a hundred miles around it. His acute
observation enables him to detect the slightest undulations of the surface,
the various changes of subsoil and alterations in the character of the
vegetation that would be quite imperceptible to a stranger. His eye is
always open to the direction in which he is going; the mossy side of trees,
the presence of certain plants under the shade of rocks, the morning and
evening flight of birds, are to him indications of direction almost as sure
as the sun in the heavens" (pp. 207, 208).
I have seen enough of savages to be able to declare that nothing can be
more admirable than this description of what a savage has to learn. But it
is incomplete. Add to all this the knowledge which a savage is obliged to
gain of the properties of plants, of the characters and habits of animals,
and of the minute indications by which their course is discoverable:
consider that even an Australian can make excellent baskets and nets, and
neatly fitted and beautifully balanced spears; that he learns to use these
so as to be able to transfix a quartern loaf at sixty yards; and that very
often, as in the case of the American Indians, the language of a savage
exhibits complexities which a well-trained European finds it difficult to
master: consider that every time a savage tracks his game he employs a
minuteness of observation, and an accuracy of inductive and deductive
reasoning which, applied to other matters, would assure some reputation to
a man of science, and I think we need ask no further why he possesses such
a fair supply of brains. In complexity and difficulty, I should say that
the intellectual labour of a "good hunter or warrior" considerably exceeds
that of an ordinary Englishman. The Civil Service Examiners are held in
great terror by young Englishmen; but even their ferocity never tempted
them to require a candidate to possess such a knowledge of a parish as Mr.
Wallace justly points out savages may possess of an area a hundred miles or
more in diameter.
But suppose, for the sake of argument, that a savage has more brains than
seems proportioned to his wants, all that can be said is that the objection
to natural selection, if it be one, applies quite as strongly to the lower
animals. The brain of a porpoise is quite wonderful for its mass, and for
the development of the cerebral convolutions. And yet since we have ceased
to credit the story of Arion, it is hard to believe that porpoises are much
troubled with intellect: and still more difficult is it to imagine that
their big brains are only a preparation for the advent of some accomplished
cetacean of the future. Surely, again, a wolf must have too much brains, or
else how is it that a dog with only the same quantity and form of brain is
able to develop such singular intelligence? The wolf stands to the dog in
the same relation as the savage to the man; and, therefore, if Mr.
Wallace's doctrine holds good, a higher power must have superintended the
breeding up of wolves from some inferior stock, in order to prepare them to
become dogs.
Mr. Wallace further maintains that the origin of some of man's mental
faculties by the preservation of useful variations is not possible. Such,
for example, are "the capacity to form ideal conceptions of space and time,
of eternity and infinity; the capacity for intense artistic feelings of
pleasure in form, colour, and composition; and for those abstract notions
of form and number which render geometry and arithmetic possible." "How,"
he asks, "were all or any of these faculties first developed, when they
could have been of no possible use to man in his early stages of
barbarism?"
Surely the answer is not far to seek. The lowest savages are as devoid of
any such conceptions as the brutes themselves. What sort of conceptions of
space and time, of form and number, can be possessed by a savage who has
not got so far as to be able to count beyond five or six, who does not know
how to draw a triangle or a circle, and has not the remotest notion of
separating the particular quality we call form, from the other qualities of
bodies? None of these capacities are exhibited by men, unless they form
part of a tolerably advanced society. And, in such a society, there are
abundant conditions by which a selective influence is exerted in favour of
those persons who exhibit an approximation towards the possession of these
capacities.
The savage who can amuse his fellows by telling a good story over the
nightly fire, is held by them in esteem and rewarded, in one way or
another, for so doing--in other words, it is an advantage to him to possess
this power. He who can carve a paddle, or the figure-head of a canoe
better, similarly profits beyond his duller neighbour. He who counts a
little better than others, gets most yams when barter is going on, and
forms the shrewdest estimate of the numbers of an opposing tribe. The
experience of daily life shows that the conditions of our present social
existence exercise the most extraordinarily powerful selective influence in
favour of novelists, artists, and strong intellects of all kinds; and it
seems unquestionable that all forms of social existence must have had the
same tendency, if we consider the indisputable facts that even animals
possess the power of distinguishing form and number, and that they are
capable of deriving pleasure from particular forms and sounds. If we admit,
as Mr. Wallace does, that the lowest savages are not raised "many grades
above the elephant and the ape;" and if we further admit, as I contend must
be admitted, that the conditions of social life tend, powerfully, to give
an advantage to those individuals who vary in the direction of intellectual
or æsthetic excellence, what is there to interfere with the belief that
these higher faculties, like the rest, owe their development to natural
selection?
Finally, with respect to the development of the moral sense out of the
simple feelings of pleasure and pain, liking and disliking, with which the
lower animals are provided, I can find nothing in Mr. Wallace's reasonings
which has not already been met by Mr. Mill, Mr. Spencer, or Mr. Darwin.
I do not propose to follow the Quarterly Reviewer and Mr. Mivart through
the long string of objections in matters of detail which they bring against
Mr. Darwin's views. Every one who has considered the matter carefully will
be able to ferret out as many more "difficulties"; but he will also, I
believe, fail as completely as they appear to me to have done, in bringing
forward any fact which is really contradictory of Mr. Darwin's views.
Occasionally, too, their objections and criticisms are based upon errors of
their own. As, for example, when Mr. Mivart and the Quarterly Reviewer
insist upon the resemblances between the eyes of _Cephalopoda_ and
_Vertebrata_, quite forgetting that there are striking and altogether
fundamental differences between them; or when the Quarterly Reviewer
corrects Mr. Darwin for saying that the gibbons, "without having been
taught, can walk or run upright with tolerable quickness, though they move
awkwardly, and much less securely than man." The Quarterly Reviewer says,
"This is a little misleading, inasmuch as it is not stated that this
upright progression is effected by placing the enormously long arms behind
the head, or holding them out backwards as a balance in progression."
Now, before carping at a small statement like this, the Quarterly Reviewer
should have made sure that he was quite right. But he happens to be quite
wrong. I suspect he got his notion of the manner in which a gibbon walks
from a citation in "Man's Place in Nature." But at that time I had not seen
a gibbon walk. Since then I have, and I can testify that nothing can be
more precise than Mr. Darwin's statement. The gibbon I saw walked without
either putting his arms behind his head or holding them out backwards. All
he did was to touch the ground with the outstretched fingers of his long
arms now and then, just as one sees a man who carries a stick, but does not
need one, touch the ground with it as he walks along.
Again, a large number of the objections brought forward by Mr. Mivart and
the Quarterly Reviewer apply to evolution in general, quite as much as to
the particular form of that doctrine advocated by Mr. Darwin; or, to their
notions of Mr. Darwin's views and not to what they really are. An excellent
example of this class of difficulties is to be found in Mr. Mivart's
chapter on "Independent Similarities of Structure." Mr. Mivart says that
these cannot be explained by an "absolute and pure Darwinian," but "that an
innate power and evolutionary law, aided by the corrective action of
natural selection, should have furnished like needs with like aids, is not
at all improbable" (p. 82).
I do not exactly know what Mr. Mivart means by an "absolute and pure
Darwinian;" indeed Mr. Mivart makes that creature hold so many singular
opinions that I doubt if I can ever have seen one alive. But I find nothing
in his statement of the view which he imagines to be originated by himself,
which is really inconsistent with what I understand to be Mr. Darwin's
views.
I apprehend that the foundation of the theory of natural selection is the
fact that living bodies tend incessantly to vary. This variation is neither
indefinite, nor fortuitous, nor does it take place in all directions, in
the strict sense of these words.
Accurately speaking, it is not indefinite, nor does it take place in all
directions, because it is limited by the general characters of the type to
which the organism exhibiting the variation belongs. A whale does not tend
to vary in the direction of producing feathers, nor a bird in the direction
of developing whalebone. In popular language there is no harm in saying
that the waves which break upon the sea-shore are indefinite, fortuitous,
and break in all directions. In scientific language, on the contrary, such
a statement would be a gross error, inasmuch as every particle of foam is
the result of perfectly definite forces, operating according to no less
definite laws. In like manner, every variation of a living form, however
minute, however apparently accidental, is inconceivable except as the
expression of the operation of molecular forces or "powers" resident within
the organism. And, as these forces certainly operate according to definite
laws, their general result is, doubtless, in accordance with some general
law which subsumes them all. And there appears to be no objection to call
this an "evolutionary law." But nobody is the wiser for doing so, or has
thereby contributed, in the least degree, to the advance of the doctrine of
evolution, the great need of which is a theory of variation.
When Mr. Mivart tells us that his "aim has been to support the doctrine
that these species have been evolved by ordinary _natural laws_ (for
the most part unknown), aided by the _subordinate_ action of 'natural
selection'" (pp. 332-3), he seems to be of opinion that his enterprise has
the merit of novelty. All I can say is that I have never had the slightest
notion that Mr. Darwin's aim is in any way different from this. If I affirm
that "species have been evolved by variation [Footnote: Including under
this head hereditary transmission.] (a natural process, the laws of which
are for the most part unknown), aided by the subordinate action of natural
selection," it seems to me that I enunciate a proposition which constitutes
the very pith and marrow of the first edition of the "Origin of Species."
And what the evolutionist stands in need of just now, is not an iteration
of the fundamental principle of Darwinism, but some light upon the
questions, What are the limits of variation? and, If a variety has arisen,
can that variety be perpetuated, or even intensified, when selective
conditions are indifferent, or perhaps unfavourable to its existence? I
cannot find that Mr. Darwin has ever been very dogmatic in answering these
questions. Formerly, he seems to have inclined to reply to them in the
negative, while now his inclination is the other way. Leaving aside those
broad questions of theology, philosophy, and ethics, by the discussion of
which neither the Quarterly Reviewer nor Mr. Mivart can be said to have
damaged Darwinism--whatever else they have injured--this is what their
criticisms come to. They confound a struggle for some rifle-pits with an
assault on the fortress.
In some respects, finally, I can only characterise the Quarterly Reviewer's
treatment of Mr. Darwin as alike unjust and unbecoming. Language of this
strength requires justification, and on that ground I add the remarks which
follow.
The Quarterly Reviewer opens his essay by a careful enumeration of all
those points upon which, during the course of thirteen years of incessant
labour, Mr. Darwin has modified his opinions. It has often and justly been
remarked, that what strikes a candid student of Mr. Darwin's works is not
so much his industry, his knowledge, or even the surprising fertility of
his inventive genius; but that unswerving truthfulness and honesty which
never permit him to hide a weak place, or gloss over a difficulty, but lead
him, on all occasions, to point out the weak places in his own armour, and
even sometimes, it appears to me, to make admissions against himself which
are quite unnecessary. A critic who desires to attack Mr. Darwin has only
to read his works with a desire to observe, not their merits, but their
defects, and he will find, ready to hand, more adverse suggestions than are
likely ever to have suggested themselves to his own sharpness, without Mr.
Darwin's self-denying aid.
Now this quality of scientific candour is not so common that it needs to be
discouraged; and it appears to me to deserve other treatment than that
adopted by the Quarterly Reviewer, who deals with Mr. Darwin as an Old
Bailey barrister deals with a man against whom he wishes to obtain a
conviction, _per fas aut nefas_, and opens his case by endeavouring to
create a prejudice against the prisoner in the minds of the jury. In his
eagerness to carry out this laudable design, the Quarterly Reviewer cannot
even state the history of the doctrine of natural selection without an
oblique and entirely unjustifiable attempt to depreciate Mr. Darwin. "To
Mr. Darwin," says he, "and (through Mr. Wallace's reticence) to Mr. Darwin
alone, is due the credit of having first brought it prominently forward and
demonstrated its truth." No one can less desire than I do, to throw a doubt
upon Mr. Wallace's originality, or to question his claim to the honour of
being one of the originators of the doctrine of natural selection; but the
statement that Mr. Darwin has the sole credit of originating the doctrine
because of Mr. Wallace's reticence is simply ridiculous. The proof of this
is, in the first place, afforded by Mr. Wallace himself, whose noble
freedom from petty jealousy in this matter smaller folk would do well to
imitate, and who writes thus:--"I have felt all my life, and I still feel,
the most sincere satisfaction that Mr. Darwin had been at work long before
me and that it was not left for me to attempt to write the 'Origin of
Species.' I have long since measured my own strength, and know well that it
would be quite unequal to that task." So that if there was any reticence at
all in the matter, it was Mr. Darwin's reticence during the long twenty
years of study which intervened between the conception and the publication
of his theory, which gave Mr. Wallace the chance of being an independent
discoverer of the importance of natural selection. And, finally, if it be
recollected that Mr. Darwin's and Mr. Wallace's essays were published
simultaneously in the "Journal of the Linnæan Society" for 1858, it follows
that the Reviewer, while obliquely depreciating Mr. Darwin's deserts, has
in reality awarded to him a priority which, in legal strictness, does not
exist.
Mr. Mivart, whose opinions so often concur with those of the Quarterly
Reviewer, puts the case in a way, which I much regret to be obliged to say,
is, in my judgment, quite as incorrect; though the injustice may be less
glaring. He says that the theory of natural selection is, in general,
exclusively associated with the name of Mr. Darwin, "on account of the
noble self-abnegation of Mr. Wallace." As I have said, no one can honour
Mr. Wallace more than I do, both for what he has done and for what he has
not done, in his relation to Mr. Darwin. And perhaps nothing is more
creditable to him than his frank declaration that he could not have written
such a work as the "Origin of Species." But, by this declaration, the
person most directly interested in the matter repudiates, by anticipation,
Mr. Mivart's suggestion that Mr. Darwin's eminence is more or less due to
Mr. Wallace's modesty.
VI
EVOLUTION IN BIOLOGY
[1878]
In the former half of the eighteenth century, the term "evolution" was
introduced into biological writings, in order to denote the mode in which
some of the most eminent physiologists of that time conceived that the
generations of living things took place; in opposition to the hypothesis
advocated, in the preceding century, by Harvey in that remarkable work
[Footnote: The _Exercitationes de Generatione Animalium_, which Dr.
George Ent extracted from him and published in 1651.] which would give him
a claim to rank among the founders of biological science, even had he not
been the discoverer of the circulation of the blood.
One of Harvey's prime objects is to defend and establish, on the basis of
direct observation, the opinion already held by Aristotle; that, in the
higher animals at any rate, the formation of the new organism by the
process of generation takes place, not suddenly, by simultaneous accretion
of rudiments of all, or of the most important, of the organs of the adult;
nor by sudden metamorphosis of a formative substance into a miniature of
the whole, which subsequently grows; but by _epigenesis_, or
successive differentiation of a relatively homogeneous rudiment into the
parts and structures which are characteristic of the adult.
"Et primò, quidem, quoniam per _epigenesin_ sive partium
superexorientium additamentum pullum fabricari certum est: quænam pars ante
alias omnes exstruatur, et quid de illa ejusque generandi modo observandum
veniat, dispiciemus. Ratum sane est et in ovo manifestè apparet quod
_Aristoteles_ de perfectorum animalium generatione enuntiat: nimirum,
non omnes partes simul fieri, sed ordine aliam post aliam; primùmque
existere particulam genitalem, cujus virtute postea (tanquam ex principio
quodam) reliquæ omnes partes prosiliant. Qualem in plantarum seminibus
(fabis, putà, aut glandibus) gemmam sive apicem protuberantem cernimus,
totius futuræ arboris principium. _Estque hæc particula, velut filius
emancipatus seorsumquc collocatus, et principium per se vivens; unde
postea, membrorum ordo describitur; et quæcunque ad absolvendum animal
pertinent, disponuntur._ [Footnote: _De Generatione Animalium_,
lib. ii. cap. x.] Quoniam enim _nulla pars se ipsam generat; sed postquam
generata est, se ipsam jam auget; ideo eam primùm oriri necesse est, quæ
principium augendi contineat (sive enim planta, sive animal est, æque
omnibus inest quod vim habeat vegetandi, sive nutriendi_), [Footnote:
_De Generatione_, lib. ii. cap. iv.] simulque reliquas omnes partes
suo quamque ordine distinguat et formet; proindeque in eadem primogenita
particula anima primario inest, sensus, motusque, et totius vitæ auctor et
principium." (Exercitatio 51.)
Harvey proceeds to contrast this view with that of the "Medici," or
followers of Hippocrates and Galen, who, "badly philosophising," imagined
that the brain, the heart, and the liver were simultaneously first
generated in the form of vesicles; and, at the same time, while expressing
his agreement with Aristotle in the principle of epigenesis, he maintains
that it is the blood which is the primal generative part, and not, as
Aristotle thought, the heart.
In the latter part of the seventeenth century, the doctrine of epigenesis,
thus advocated by Harvey, was controverted, on the ground of direct
observation, by Malpighi, who affirmed that the body of the chick is to be
seen in the egg, before the _punctum sanguineum_ makes it appearance.
But, from this perfectly correct observation a conclusion which is by no
means warranted was drawn; namely, that the chick, as a whole, really
exists in the egg antecedently to incubation; and that what happens in the
course of the latter process is no addition of new parts, "alias post alias
natas," as Harvey puts it, but a simple expansion, or unfolding, of the
organs which already exist, though they are too small and inconspicuous to
be discovered. The weight of Malpighi's observations therefore fell into
the scale of that doctrine which Harvey terms _metamorphosis_, in
contradistinction to epigenesis.
The views of Malpighi were warmly welcomed, on philosophical grounds, by
Leibnitz, [Footnote: "Cependant, pour revenir aux formes ordinaires ou aux
âmes matérielles, cette durée qu'il leur faut attribuer à la place de celle
qu'on avoit attribuée aux atomes pourroit faire douter si elles ne vont pas
de corps en corps; ce qui seroit la métempsychose, à peu près comme
quelques philosophes ont cru la transmission du mouvement et celle des
espèces. Mais cette imagination est bien éloignée de la nature des choses.
Il n'y a point de tel passage; et c'est ici où les transformations de
Messieurs Swammerdam, Malpighi, et Leewenhoek, qui sont des plus excellens
observateurs de notre tems, sont venues à mon secours, et m'ont fait
admettre plus aisément, que l'animal, et toute autre substance organisée ne
commence point lorsque nous le croyons, et que sa generation apparente
n'est qu'une développement et une espèce d'augmentation. Aussi ai je
remarqué que l'auteur de la _Recherche de la Verité_, M. Regis, M.
Hartsoeker, et d'autres habiles hommes n'ont pas été fort éloignés de ce
sentiment." Leibnitz, _Système Nouveau de la Nature_, 1695. The
doctrine of "Embôitement" is contained in the _Considérations sur le
Principe de Vie_, 1705; the preface to the _Theodicée_, 1710; and
the _Principes de la Nature et de la Grace_ (§ 6), 1718.] who found in
them a support to his hypothesis of monads, and by Malebranche; [Footnote:
"Il est vrai que la pensée la plus raisonnable et la plus conforme à
l'experience sur cette question très difficile de la formation du foetus;
c'est que les enfans sont déja presque tout formés avant même l'action par
laquelle ils sont conçus; et que leurs mères ne font que leur donner
l'accroissement ordinaire dans le temps de la grossesse." _De la
Recherche de la Verité_, livre ii. chap. vii. p. 334, 7th ed., 1721.]
while, in the middle of the eighteenth century, not only speculative
considerations, but a great number of new and interesting observations on
the phenomena of generation, led the ingenious Bonnet, and Haller,
[Footnote: The writer is indebted to Dr. Allen Thomson for reference to the
evidence contained in a note to Haller's edition of Boerhaave's
_Prælectiones Academicæ_, vol. v. pt. ii. p. 497, published in 1744,
that Haller originally advocated epigenesis.] the first physiologist of the
age, to adopt, advocate, and extend them.
Bonnet affirms that, before fecundation, the hen's egg contains an
excessively minute but complete chick; and that fecundation and incubation
simply cause this germ to absorb nutritious matters, which are deposited in
the interstices of the elementary structures of which the miniature chick,
or germ, is made up. The consequence of this intussusceptive growth is the
"development" or "evolution" of the germ into the visible bird. Thus an
organised individual (_tout organisé_) "is a composite body consisting
of the original, or _elementary_, parts and of the matters which have
been associated with them by the aid of nutrition;" so that, if these
matters could be extracted from the individual (_tout_), it would, so
to speak, become concentrated in a point, and would thus be restored to its
primitive condition of a _germ_; "just as by extracting from a bone
the calcareous substance which is the source of its hardness, it is reduced
to its primitive state of gristle or membrane." [Footnote:
_Considérations sur les Corps organisés, chap. x.] "Evolution" and
"development" are, for Bonnet, synonymous terms; and since by "evolution"
he means simply the expansion of that which was invisible into visibility,
he was naturally led to the conclusion, at which Leibnitz had arrived by a
different line of reasoning, that no such thing as generation, in the
proper sense of the word, exists in Nature. The growth of an organic being
is simply a process of enlargement as a particle of dry gelatine may be
swelled up by the intussusception of water; its death is a shrinkage, such
as the swelled jelly might undergo on desiccation. Nothing really new is
produced in the living world, but the germs which develop have existed
since the beginning of things; and nothing really dies, but, when what we
call death takes place, the living thing shrinks back into its germ state.
[Footnote: Bonnet had the courage of his opinions, and in the
_Palingénésie Philosophique_, part vi. chap, iv., he develops a
hypothesis which he terms "évolution naturelle;" and which, making
allowance for his peculiar views of the nature of generation, bears no
small resemblance to what is understood by "evolution" at the present
day:--
"Si la volonté divine a créé par un seul Acte l'Universalité des êtres,
d'où venoient ces plantes et ces animaux dont Moyse nous decrit la
Production au troisieme et au cinquieme jour du renouvellement de notre
monde?
"Abuserois-je de la liberté de conjectures si je disois, que les Plantes et
les Animaux qui existent aujourd'hui sont parvenus par une sorte
d'evolution naturelle des Etres organises qui peuplaient ce premier Monde,
sorti immédiatement des MAINS du CREATEUR?...
"Ne supposons que trois révolutions. La Terre vient de sortir des MAINS du
CREATEUR. Des causes preparées par sa SAGESSE font développer de toutes
parts les Germes. Les Etres organisés commencent à jouir de l'existence.
Ils étoient probablement alors bien différens de ce qu'ils sont
aujourd'hui. Ils l'etoient autant que ce premier Monde différoit de celui
que nous habitons. Nous manquons de moyens pour juger de ces dissemblances,
et peut-être que le plus habile Naturaliste qui auroit été placé dans ce
premier Monde y auroit entièrement méconnu nos Plantes et nos Animaux."]
The two parts of Bonnet's hypothesis, namely, the doctrine that all living
things proceed from pre-existing germs, and that these contain, one
inclosed within the other, the germs of all future living things, which is
the hypothesis of "_emboîtement_;" and the doctrine that every germ
contains in miniature all the organs of the adult, which is the hypothesis
of evolution or development, in the primary senses of these words, must be
carefully distinguished. In fact, while holding firmly by the former,
Bonnet more or less modified the latter in his later writings, and, at
length, he admits that a "germ" need not be an actual miniature of the
organism; but that it may be merely an "original preformation" capable of
producing the latter. [Footnote: "Ce mot (germe) ne désignera pas seulement
un corps organisé _réduit en petit_; il désignera encore toute espèce
de _préformation originelle dont un Tout organique peut résulter comme de
son principe immédiat."--Palingénésie Philosophique_, part X. chap. II.]
But, thus defined, the germ is neither more nor less than the "particula
genitalis" of Aristotle, or the "primordium vegetale" or "ovum" of Harvey;
and the "evolution" of such a germ would not be distinguishable from
"epigenesis."
Supported by the great authority of Haller, the doctrine of evolution, or
development, prevailed throughout the whole of the eighteenth century, and
Cuvier appears to have substantially adopted Bonnet's later views, though
probably he would not have gone all lengths in the direction of
"emboîtement." In a well-known note to Laurillard's "Éloge," prefixed to
the last edition of the "Ossemens fossiles," the "radical de l'être" is
much the same thing as Aristotle's "particula genitalis" and Harvey's
"ovum." [Footnote: "M. Cuvier considérant que tous les êtres organisés sont
dérivés de parens, et ne voyant dans la nature aucune force capable de
produire l'organisation, croyait à la pré-existence des germes; non pas à
la pré-existence d'un être tout formé, puisqu'il est bien évident que ce
n'est que par des développemens successifs que l'être acquiert sa forme;
mais, si l'on peut s'exprimer ainsi, à la pré-existence du _radical de
l'être_, radical qui existe avant que la série des évolutions ne
commence, et qui remonte certainement, suivant la belle observation de
Bonnet, à plusieurs generations."--Laurillard, _Éloge de Cuvier_, note
12.]
Bonnet's eminent contemporary, Buffon, held nearly the same views with
respect to the nature of the germ, and expresses them even more
confidently.
"Ceux qui ont cru que le coeur étoit le premier formé, se sont trompés;
ceux qui disent que c'est le sang se trompent aussi: tout est formé en même
temps. Si l'on ne consulte que l'observation, le poulet se voit dans l'oeuf
avant qu'il ait été couvé." [Footnote: _Histoire Naturelle_, tom. ii.
ed. ii. 1750, p. 350.]
"J'ai ouvert une grande quantité d'oeufs à differens temps avant et après
l'incubation, et je me suis convaincu par mes yeux que le poulet existe en
entier dans le milieu de la cicatricule au moment qu'il sort du corps de la
poule." [Footnote: _Ibid_., p. 351.]
The "moule intérieur" of Buffon is the aggregate of elementary parts which
constitute the individual, and is thus the equivalent of Bonnet's germ,
[Footnote: See particularly Buffon, _l. c._ p. 41.] as defined in the
passage cited above. But Buffon further imagined that innumerable
"molecules organiques" are dispersed throughout the world, and that
alimentation consists in the appropriation by the parts of an organism of
those molecules which are analogous to them. Growth, therefore, was, on
this hypothesis, a process partly of simple evolution, and partly of what
has been termed "syngenesis." Buffon's opinion is, in fact, a sort of
combination of views, essentially similar to those of Bonnet, with others,
somewhat similar to those of the "Medici" whom Harvey condemns. The
"molecules organiques" are physical equivalents of Leibnitz's "monads."
It is a striking example of the difficulty of getting people to use their
own powers of investigation accurately, that this form of the doctrine of
evolution should have held its ground so long; for it was thoroughly and
completely exploded, not long after its enunciation, by Casper Friederich
Wolff, who in his "Theoria Generationis," published in 1759, placed the
opposite theory of epigenesis upon the secure foundation of fact, from
which it has never been displaced. But Wolff had no immediate successors.
The school of Cuvier was lamentably deficient in embryologists; and it was
only in the course of the first thirty years of the present century, that
Prévost and Dumas in France, and, later on, Döllinger, Pander, Von Bär,
Rathke, and Remak in Germany, founded modern embryology; while, at the same
time, they proved the utter incompatibility of the hypothesis of evolution,
as formulated by Bonnet and Haller, with easily demonstrable facts.
Nevertheless, though the conceptions originally denoted by "evolution" and
"development" were shown to be untenable, the words retained their
application to the process by which the embryos of living beings gradually
make their appearance; and the terms "Development," "Entwickelung," and
"Evolutio," are now indiscriminately used for the series of genetic changes
exhibited by living beings, by writers who would emphatically deny that
"Development" or "Entwickelung" or "Evolutio," in the sense in which these
words were usually employed by Bonnet or by Haller, ever occurs.
Evolution, or development, is, in fact, at present employed in biology as a
general name for the history of the steps by which any living being has
acquired the morphological and the physiological characters which
distinguish it. As civil history may be divided into biography, which is
the history of individuals, and universal history, which is the history of
the human race, so evolution falls naturally into two categories--the
evolution of the individual, and the evolution of the sum of living beings.
It will be convenient to deal with the modern doctrine of evolution under
these two heads.
I. _The Evolution of the Individual_.
No exception is at this time, known to the general law, established upon an
immense multitude of direct observations, that every living thing is
evolved from a particle of matter in which no trace of the distinctive
characters of the adult form of that living thing is discernible. This
particle is termed a _germ_. Harvey [Footnote: _Execitationes de
Generatione_. Ex. 62, "Ovum esse primordium commune omnibus
animalibus."] says--
"Omnibus viventibus primordium insit, ex quo et a quo proveniant. Liceat
hoc nobis _primordium vegetale_ nominare; nempe substantiam quandam
corpoream vitam habentem potentiâ; vel quoddam per se existens, quod aptum
sit, in vegetativam formam, ab interno principio operante, mutari. Quale
nempe primordium, ovum est et plantarum semen; tale etiam viviparorum
conceptus, et insectorum _vermis_ ab Aristotele dictus: diversa
scilicet diversorum viventium primordia."
The definition of a germ as "matter potentially alive, and having within
itself the tendency to assume a definite living form," appears to meet all
the requirements of modern science. For, notwithstanding it might be justly
questioned whether a germ is not merely potentially, but rather actually,
alive, though its vital manifestations are reduced to a minimum, the term
"potential" may fairly be used in a sense broad enough to escape the
objection. And the qualification of "potential" has the advantage of
reminding us that the great characteristic of the germ is not so much what
it is, but what it may, under suitable conditions, become. Harvey shared
the belief of Aristotle--whose writings he so often quotes and of whom he
speaks as his precursor and model, with the generous respect with which one
genuine worker should regard another--that such germs may arise by a
process of "equivocal generation" out of not-living matter; and the
aphorism so commonly ascribed to him, "_omne vivum ex ovo_" and which
is indeed a fair summary of his reiterated assertions, though incessantly
employed against the modern advocates of spontaneous generation, can be
honestly so used only by those who have never read a score of pages of the
"Exercitationes." Harvey, in fact, believed as implicitly as Aristotle did
in the equivocal generation of the lower animals. But, while the course of
modern investigation has only brought out into greater prominence the
accuracy of Harvey's conception of the nature and mode of development of
germs, it has as distinctly tended to disprove the occurrence of equivocal
generation, or abiogenesis, in the present course of nature. In the immense
majority of both plants and animals, it is certain that the germ is not
merely a body in which life is dormant or potential, but that it is itself
simply a detached portion of the substance of a pre-existing living body;
and the evidence has yet to be adduced which will satisfy any cautious
reasoner that "omne vivum ex vivo" is not as well-established a law of the
existing course of nature as "omne vivum ex ovo."
In all instances which have yet been investigated, the substance of this
germ has a peculiar chemical composition, consisting of at fewest four
elementary bodies, viz., carbon, hydrogen, oxygen, and nitrogen, united
into the ill-defined compound known as protein, and associated with much
water, and very generally, if not always, with sulphur and phosphorus in
minute proportions. Moreover, up to the present time, protein is known only
as a product and constituent of living matter. Again, a true germ is either
devoid of any structure discernible by optical means, or, at most, it is a
simple nucleated cell. [Footnote: In some cases of sexless multiplication
the germ is a cell-aggregate--if we call germ only that which is already
detached from the parent organism.]
In all cases the process of evolution consists in a succession of changes
of the form, structure, and functions of the germ, by which it passes, step
by step, from an extreme simplicity, or relative homogeneity, of visible
structure, to a greater or less degree of complexity or heterogeneity; and
the course of progressive differentiation is usually accompanied by growth,
which is effected by intussusception. This intussusception, however, is a
very different process from that imagined either by Buffon or by Bonnet.
The substance by the addition of which the germ is enlarged is in no case
simply absorbed, ready-made, from the not-living world and packed between
the elementary constituents of the germ, as Bonnet imagined; still less
does it consist of the "molecules organiques" of Buffon. The new material
is, in great measure, not only absorbed but assimilated, so that it becomes
part and parcel of the molecular structure of the living body into which it
enters. And, so far from the fully developed organism being simply the germ
_plus_ the nutriment which it has absorbed, it is probable that the
adult contains neither in form, nor in substance, more than an
inappreciable fraction of the constituents of the germ, and that it is
almost, if not wholly, made up of assimilated and metamorphosed nutriment.
In the great majority of cases, at any rate, the full-grown organism
becomes what it is by the absorption of not-living matter, and its
conversion into living matter of a specific type. As Harvey says (Ex. 45),
all parts of the body are nourished "ab eodem succo alibili, aliter
aliterque cambiato," "ut plantæ omnes ex eodem communi nutrimento (sive
rore seu terræ humore)."
In all animals and plants above the lowest the germ is a nucleated cell,
using that term in its broadest sense; and the first step in the process of
the evolution of the individual is the division of this cell into two or
more portions. The process of division is repeated, until the organism,
from being unicellular, becomes multicellular. The single cell becomes a
cell-aggregate; and it is to the growth and metamorphosis of the cells of
the cell-aggregate thus produced, that all the organs and tissues of the
adult owe their origin.
In certain animals belonging to every one of the chief groups into which
the _Metazoa_ are divisible, the cells of the cell-aggregate which
results from the process of yelk-division, and which is termed a
_morula_, diverge from one another in such a manner as to give rise to
a central space, around which they dispose themselves as a coat or
envelope; and thus the morula becomes a vesicle filled with fluid, the
_planula_. The wall of the planula is next pushed in on one side, or
invaginated, whereby it is converted into a double-walled sac with an
opening, the _blastopore_, which leads into the cavity lined by the
inner wall. This cavity is the primitive alimentary cavity or
_archenteron_; the inner or invaginated layer is the _hypoblast_;
the outer the _epiblast_; and the embryo, in this stage, is termed a
_gastrula_. In all the higher animals a layer of cells makes its
appearance between the hypoblast and the epiblast, and is termed the
_mesoblast_. In the further course of development the epiblast becomes
the ectoderm or epidermic layer of the body; the hypoblast becomes the
epithelium of the middle portion of the alimentary canal; and the mesoblast
gives rise to all the other tissues, except the central nervous system,
which originates from an ingrowth of the epiblast.
With more or less modification in detail, the embryo has been observed to
pass through these successive evolutional stages in sundry Sponges,
Coelenterates, Worms, Echinoderms, Tunicates, Arthropods, Mollusks, and
Vertebrates; and there are valid reasons for the belief that all animals of
higher organisation than the _Protozoa_, agree in the general
character of the early stages of their individual evolution. Each, starting
from the condition of a simple nucleated cell, becomes a cell-aggregate;
and this passes through a condition which represents the gastrula stage,
before taking on the features distinctive of the group to which it belongs.
Stated in this form, the "gastræa theory" of Haeckel appears to the present
writer to be one of most important and best founded of recent
generalisations. So far as individual plants and animals are concerned,
therefore, evolution is not a speculation but a fact; and it takes place by
epigenesis.
"Animal...per _epigenesin_ procreatur, materiam simul attrahit, parat,
concoquit, et eâdem utitur; formatur simul et augetur ... primum futuri
corporis concrementum ... prout augetur, dividitur sensim et distinguitur
in partes, non simul omnes, sed alias post alias natas, et ordine quasque
suo emergentes." [Footnote: Harvey, _Exercitationes de Generatione_.
Ex. 45, "Quænam sit pulli materia et quomodo fiat in Ovo."] In these words,
by the divination of genius, Harvey, in the seventeenth century, summed up
the outcome of the work of all those who, with appliances he could not
dream of, are continuing his labours in the nineteenth century.
Nevertheless, though the doctrine of epigenesis, as understood by Harvey,
has definitively triumphed over the doctrine of evolution, as understood by
his opponents of the eighteenth century, it is not impossible that, when
the analysis of the process of development is carried still further, and
the origin of the molecular components of the physically gross, though
sensibly minute, bodies which we term germs is traced, the theory of
development will approach more nearly to metamorphosis than to epigenesis.
Harvey thought that impregnation influenced the female organism as a
contagion; and that the blood, which he conceived to be the first rudiment
of the germ, arose in the clear fluid of the "colliquamentum" of the ovum
by a process of concrescence, as a sort of living precipitate. We now know,
on the contrary, that the female germ or ovum, in all the higher animals
and plants, is a body which possesses the structure of a nucleated cell;
that impregnation consists in the fusion of the substance [Footnote: [At
any rate of the nuclei of the two germ-cells. 1893]] of another more or
less modified nucleated cell, the male germ, with the ovum; and that the
structural components of the body of the embryo are all derived, by a
process of division, from the coalesced male and female germs. Hence it is
conceivable, and indeed probable, that every part of the adult contains
molecules, derived both from the male and from the female parent; and that,
regarded as a mass of molecules, the entire organism may he compared to a
web of which the warp is derived from the female and the woof from the
male. And each of these may constitute one individuality, in the same sense
as the whole organism is one individual, although the matter of the
organism has been constantly changing. The primitive male and female
molecules may play the part of Buffon's "moules organiques," and mould the
assimilated nutriment, each according to its own type, into innumerable new
molecules. From this point of view the process, which, in its superficial
aspect, is epigenesis, appears in essence, to be evolution, in the modified
sense adopted in Bonnet's later writings; and development is merely the
expansion of a potential organism or "original preformation" according to
fixed laws.
II. _The Evolution of the Sum of Living Beings_.
The notion that all the kinds of animals and plants may have come into
existence by the growth and modification of primordial germs is as old as
speculative thought; but the modern scientific form of the doctrine can be
traced historically to the influence of several converging lines of
philosophical speculation and of physical observation, none of which go
farther back than the seventeenth century. These are:--
1. The enunciation by Descartes of the conception that the physical
universe, whether living or not living, is a mechanism, and that, as such,
it is explicable on physical principles.
2. The observation of the gradations of structure, from extreme simplicity
to very great complexity, presented by living things, and of the relation
of these graduated forms to one another.
3. The observation of the existence of an analogy between the series of
gradations presented by the species which compose any great group of
animals or plants, and the series of embryonic conditions of the highest
members of that group.
4. The observation that large groups of species of widely different habits
present the same fundamental plan of structure; and that parts of the same
animal or plant, the functions of which are very different, likewise
exhibit modifications of a common plan.
5. The observation of the existence of structures, in a rudimentary and
apparently useless condition, in one species of a group, which are fully
developed and have definite functions in other species of the same group.
6. The observation of the effects of varying conditions in modifying living
organisms.
7. The observation of the facts of geographical distribution.
8. The observation of the facts of the geological succession of the forms
of life.
1. Notwithstanding the elaborate disguise which fear of the powers that
were led Descartes to throw over his real opinions, it is impossible to
read the "Principes de la Philosophie" without acquiring the conviction
that this great philosopher held that the physical world and all things in
it, whether living or not living, have originated by a process of
evolution, due to the continuous operation of purely physical causes, out
of a primitive relatively formless matter. [Footnote: As Buffon has well
said:--"L'idée de ramener l'explication de tous les phénomènes à des
principes mecaniques est assurement grande et belle, ce pas est le plus
hardi qu'on peut faire en philosophie, et c'est Descartes qui l'a
fait."--_l. c._ p. 50.]
The following passage is especially instructive:--
"Et tant s'en faut que je veuille que l'on croie toutes les choses que
j'écrirai, que même je pretends en proposer ici quelques unes que je crois
absolument être fausses; à savoir, je ne doute point quo le monde n'ait été
créé au commencement avec autant de perfection qu'il eu a; en sorte que le
soleil, la terre, la lune, et les étoiles ont été dès lors; et que la terre
n'a pas eu seulement en soi les semences des plantes, mais que les plantes
même en ont couvert une partie; et qu' Adam et Eve n'ont pas été créés
enfans mais en âge d'hommes parfaits. La religion chrétienne veut que nous
le croyons ainsi, et la raison naturelle nous persuade entièrement cette
vérité; car si nous considérons la toute puissance de Dieu, nous devons
juger que tout ce qu'il a fait a eu dès le commencement toute la perfection
qu'il devoit avoir. Mais néanmoins, comme on connôitroit beaucoup mieux
quelle a été la nature d'Adam et celle des arbres de Paradis si on avoit
examiné comment les enfants se forment peu à peu dans le ventre de leurs
mères et comment les plantes sortent de leurs semences, que si on avoit
seulement considéré quels ils ont été quand Dieu les a créés: tout de même,
nous ferons mieux entendre quelle est généralement la nature de toutes les
choses qui sont au monde si nous pouvons imaginer quelques principes qui
soient fort intelligibles et fort simples, desquels nous puissions voir
clairement que les astres et la terre et enfin tout ce monde visible auroit
pu être produit ainsi que de quelques semences (bien que, nous sachions
qu'il n'a pas été produit en cette façon) que si nous la decrivions
seulement comme il est, ou bien comme nous croyons qu'il a été créé. Et
parceque je pense avoir trouvé des principes qui sont tels, je tacherai ici
de les expliquer." [Footnote: _Principes de la Philosophie_, Troisième
partie, § 45.]
If we read between the lines of this singular exhibition of force of one
kind and weakness of another, it is clear that Descartes believed that he
had divined the mode in which the physical universe had been evolved; and
the "Traité de l'Homme," and the essay "Sur les Passions" afford abundant
additional evidence that he sought for, and thought he had found, an
explanation of the phenomena of physical life by deduction from purely
physical laws.
Spinoza abounds in the same sense, and is as usual perfectly candid--
"Naturæ leges et regulæ, secundum quas omnia fiunt et ex unis formis in
alias mutantur, sunt ubique et semper eadem." [Footnote: _Ethices_,
Pars tertia, Præfatio.] Leibnitz's doctrine of continuity necessarily led
him in the same direction; and, of the infinite multitude of monads with
which he peopled the world, each is supposed to be the focus of an endless
process of evolution and involution. In the "Protogæa," xxvi., Leibnitz
distinctly suggests the mutability of species--
"Alii mirantur in saxis passim species videri quas vel in orbe cognito, vel
saltem in vicinis locis frustra quæras. 'Ita Cornua Ammonis,' quæ ex
nautilorum numero habeantur, passim et forma et magnitudine (nam et pedali
diametro aliquando reperiuntur) ab omnibus illis naturis discrepare dicunt,
quas præbet mare. Sed quis absconditos ejus recessus aut subterraneas
abyssos pervestigavit? quam multa nobis animalia antea ignota offert novus
orbis? Et credibile est per magnas illas conversiones etiam animalium
species plurimum immutatas."
Thus, in the end of the seventeenth century, the seed was sown which has,
at intervals, brought forth recurrent crops of evolutional hypotheses,
based, more or less completely, on general reasonings.
Among the earliest of these speculations is that put forward by Benoit de
Maillet in his "Telliamed," which, though printed in 1735, was not
published until twenty-three years later. Considering that this book was
written before the time of Haller, or Bonnet, or Linnæus, or Hutton, it
surely deserves more respectful consideration than it usually receives. For
De Maillet not only has a definite conception of the plasticity of living
things, and of the production of existing species by the modification of
their predecessors; but he clearly apprehends the cardinal maxim of modern
geological science, that the explanation of the structure of the globe is
to be sought in the deductive application to geological phenomena of the
principles established inductively by the study of the present course of
nature. Somewhat later, Maupertuis [Footnote: _Système de la Nature_.
"Essai sur la Formation des Corps Organisés," 1751, xiv.] suggested a
curious hypothesis as to the causes of variation, which he thinks may be
sufficient to account for the origin of all animals from a single pair.
Robinet [Footnote: _Considérations Philosophiques sur la gradation
naturelle des formes de l'être; ou les essais de la nature qui apprend a
faire l'homme,_ 1768.] followed out much the same line of thought as De
Maillet, but less soberly; and Bonnet's speculations in the "Palingénésie,"
which appeared in 1769, have already been mentioned. Buffon (1753-1778), at
first a partisan of the absolute immutability of species, subsequently
appears to have believed that larger or smaller groups of species have been
produced by the modification of a primitive stock; but he contributed
nothing to the general doctrine of evolution.
Erasmus Darwin ("Zoonomia," 1794), though a zealous evolutionist, can
hardly be said to have made any real advance on his predecessors; and,
notwithstanding that Goethe (1791-4) had the advantage of a wide knowledge
of morphological facts, and a true insight into their signification, while
he threw all the power of a great poet into the expression of his
conceptions, it may be questioned whether he supplied the doctrine of
evolution with a firmer scientific basis than it already possessed.
Moreover, whatever the value of Goethe's labours in that field, they were
not published before 1820, long after evolutionism had taken a new
departure from the works of Treviranus and Lamarck--the first of its
advocates who were equipped for their task with the needful large and
accurate knowledge of the phenomena of life, as a whole. It is remarkable
that each of these writers seems to have been led, independently and
contemporaneously, to invent the same name of "Biology" for the science of
the phenomena of life; and thus, following Buffon, to have recognised the
essential unity of these phenomena, and their contradistinction from those
of inanimate nature. And it is hard to say whether Lamarck or Treviranus
has the priority in propounding the main thesis of the doctrine of
evolution; for though the first volume of Treviranus's "Biologie" appeared
only in 1802, he says, in the preface to his later work, the "Erscheinungen
und Gesetze des organischen Lebens," dated 1831, that he wrote the first
volume of the "Biologie" "nearly five-and-thirty years ago," or about 1796.
Now, in 1794, there is evidence that Lamarck held doctrines which present a
striking contrast to those which are to be found in the "Philosophie
Zoologique," as the following passages show:--
"685. Quoique mon unique objet dans cet article n'ait été que de traiter de
la cause physique de l'entretien de la vie des êtres organiques, malgré
cela j'ai osé avancer en débutant, que l'existence de ces êtres étonnants
n'appartiennent nullement à la nature; que tout ce qu'on peut entendre par
le mot _nature_, ne pouvoit donner la vie, c'est-à-dire, que toutes
les qualités de la matière, jointes à toutes les circonstances possibles,
et même à l'activité répandue dans l'univers, ne pouvaient point produire
un être muni du mouvement organique, capable de reproduire son semblable,
et sujet à la mort.
"686. Tous les individus de cette nature, qui existent, proviennent
d'individus semblables qui tous ensemble constituent l'espèce entière. Or,
je crois qu'il est aussi impossible à l'homme de connôitre la cause
physique du premier individu de chaque espèce, que d'assigner aussi
physiquement la cause de l'existence de la matière ou de l'univers entier.
C'est au moins ce que le résultat de mes connaissances et de mes réflexions
me portent à penser. S'il existe beaucoup de variétés produites par l'effet
des circonstances, ces variétés ne denaturent point les espèces; mais on se
trompe, sans doute souvent, en indiquant comme espèce, ce qui n'est que
variété; et alors je sens que cette erreur peut tirer à conséquence dans
les raisonnements que l'on fait sur cette matière." [Footnote:
_Recherches sur les causes des principaux faits physiques_, par J.B.
Lamarck. Paris. Seconde année de la République. In the preface, Lamarck
says that the work was written in 1776, and presented to the Academy in
1780; but it was not published before 17994, and, at that time, it
presumably expressed Lamarck's mature views. It would be interesting to
know what brought about the change of opinion manifested in the
_Recherches sur l'organisation des corps vivants_, published only
seven years later.]
The first three volumes of Treviranus's "Biologie," which contain his
general views of evolution, appeared between 1802 and 1805. The "Recherches
sur l'organisation des corps vivants," in which the outlines of Lamarck's
doctrines are given, was published in 1802, but the full development of his
views, in the "Philosophie Zoologique," did not take place until 1809.
The "Biologie" and the "Philosophie Zoologique" are both very remarkable
productions, and are still worthy of attentive study, but they fell upon
evil times. The vast authority of Cuvier was employed in support of the
traditionally respectable hypotheses of special creation and of
catastrophism; and the wild speculations of the "Discours sur les
Révolutions de la Surface du Globe" were held to be models of sound
scientific thinking, while the really much more sober and philosophical
hypotheses of the "Hydrogeologie" were scouted. For many years it was the
fashion to speak of Lamarck with ridicule, while Treviranus was altogether
ignored.
Nevertheless, the work had been done. The conception of evolution was
henceforward irrepressible, and it incessantly reappears, in one shape or
another, [Footnote: See the "Historical Sketch" prefixed to the last
edition of the _Origin of Species_.] up to the year 1858, when Mr.
Darwin and Mr. Wallace published their "Theory of Natural Selection." The
"Origin of Species" appeared in 1859; and it is within the knowledge of all
whose memories go back to that time, that, henceforward, the doctrine of
evolution has assumed a position and acquired an importance which it never
before possessed. In the "Origin of Species," and in his other numerous and
important contributions to the solution of the problem of biological
evolution, Mr. Darwin confines himself to the discussion of the causes
which have brought about the present condition of living matter, assuming
such matter to have once come into existence. On the other hand, Mr.
Spencer [Footnote: _First Principles_. and _Principles of
Biology_, 1860-1864.] and Professor Haeckel [Footnote: _Generelle
Marphologie_, 1866.] have dealt with the whole problem of evolution. The
profound and vigorous writings of Mr. Spencer embody the spirit of
Descartes in the knowledge of our own day, and may be regarded as the
"Principes de la Philosophie" of the nineteenth century; while, whatever
hesitation may not unfrequently be felt by less daring minds, in following
Haeckel in many of his speculations, his attempt to systematise the
doctrine of evolution and to exhibit its influence as the central thought
of modern biology, cannot fail to have a far-reaching influence on the
progress of science.
If we seek for the reason of the difference between the scientific position
of the doctrine of evolution a century ago, and that which it occupies now,
we shall find it in the great accumulation of facts, the several classes of
which have been enumerated above, under the second to the eighth heads. For
those which are grouped under the second to the seventh of these classes,
respectively, have a clear significance on the hypothesis of evolution,
while they are unintelligible if that hypothesis be denied. And those of
the eighth group are not only unintelligible without the assumption of
evolution, but can be proved never to be discordant with that hypothesis,
while, in some cases, they are exactly such as the hypothesis requires. The
demonstration of these assertions would require a volume, but the general
nature of the evidence on which they rest may be briefly indicated.
2. The accurate investigation of the lowest forms of animal life, commenced
by Leeuwenhoek and Swammerdam, and continued by the remarkable labours of
Reaumur, Trembley, Bonnet, and a host of other observers, in the latter
part of the seventeenth and the first half of the eighteenth centuries,
drew the attention of biologists to the gradation in the complexity of
organisation which is presented by living beings, and culminated in the
doctrine of the "échelle des êtres," so powerfully and clearly stated by
Bonnet; and, before him, adumbrated by Locke and by Leibnitz. In the then
state of knowledge, it appeared that all the species of animals and plants
could be arranged in one series; in such a manner that, by insensible
gradations, the mineral passed into the plant, the plant into the polype,
the polype into the worm, and so, through gradually higher forms of life,
to man, at the summit of the animated world.
But, as knowledge advanced, this conception ceased to be tenable in the
crude form in which it was first put forward. Taking into account existing
animals and plants alone, it became obvious that they fell into groups
which were more or less sharply separated from one another; and, moreover,
that even the species of a genus can hardly ever be arranged in linear
series. Their natural resemblances and differences are only to be expressed
by disposing them as if they were branches springing from a common
hypothetical centre.
Lamarck, while affirming the verbal proposition that animals form a single
series, was forced by his vast acquaintance with the details of zoology to
limit the assertion to such a series as may be formed out of the
abstractions constituted by the common characters of each group. [Footnote:
"Il s'agit donc de prouver que la série qui constitue l'échelle animale
réside essentiellement dans la distribution des masses principales qui la
composent et non dans celle des espèces ni même toujours dans celle des
genres."--_Philosophie Zoologique_. chap. v.]
Cuvier on anatomical, and Von Baer on embryological grounds, made the
further step of proving that, even in this limited sense, animals cannot be
arranged in a single series, but that there are several distinct plans of
organisation to be observed among them, no one of which, in its highest and
most complicated modification, leads to any of the others.
The conclusions enunciated by Cuvier and Von Baer have been confirmed, in
principle, by all subsequent research into the structure of animals and
plants. But the effect of the adoption of these conclusions has been rather
to substitute a new metaphor for that of Bonnet than to abolish the
conception expressed by it. Instead of regarding living things as capable
of arrangement in one series like the steps of a ladder, the results of
modern investigation compel us to dispose them as if they were the twigs
and branches of a tree. The ends of the twigs represent individuals, the
smallest groups of twigs species, larger groups genera, and so on, until we
arrive at the source of all these ramifications of the main branch, which
is represented by a common plan of structure. At the present moment, it is
impossible to draw up any definition, based on broad anatomical or
developmental characters, by which any one of Cuvier's great groups shall
be separated from all the rest. On the contrary, the lower members of each
tend to converge towards the lower members of all the others. The same may
be said of the vegetable world. The apparently clear distinction between
flowering and flowerless plants has been broken down by the series of
gradations between the two exhibited by the _Lycopodiaceæ,
Rhizocarpeæ_, and _Gymnospermeæ_. The groups of _Fungi_,
_Lichenes_, and _Algæ_ have completely run into one another, and,
when the lowest forms of each are alone considered, even the animal and
vegetable kingdoms cease to have a definite frontier.
If it is permissible to speak of the relations of living forms to one
another metaphorically, the similitude chosen must undoubtedly be that of a
common root, whence two main trunks, one representing the vegetable and one
the animal world, spring; and, each dividing into a few main branches,
these subdivide into multitudes of branchlets and these into smaller groups
of twigs.
As Lamarck has well said--[Footnote: _Philosophie Zoologique_,
première partie, chap. iii.] "Il n'y a que ceux qui se sont longtemps et
fortement occupés de la détermination des espèces, et qui ont consulté de
riches collections, qui peuvent savoir jusqu'à quel point les
_espèces_, parmi les corps vivants se fondent les unes dans les
autres, et qui ont pu se convaincre que, dans les parties où nous voyons
des _espèces_ isolès, cela n'est ainsi que parcequ'il nous en manque
d'autres qui en sont plus voisines et que nous n'avons pas encore
recueillies.
"Je ne veux pas dire pour cela que les animaux qui existent forment une
série très-simple et partout également nuancée; mais je dis qu'ils forment
une série ramense, irréguliérement graduée et qui n'a point de
discontinuité dans ses parties, ou qui, du moins, n'en a toujours pas eu,
s'il est vrai que, par suite de quelques espèces perdues, il s'en trouve
quelque part. Il en resulte que les _espèces_ qui terminent chaque
rameau de la série générale tiennent, au moins d'un côté, à d'autres
espèces voisines qui se nuancent avec elles. Voilà ce que l'état bien connu
des choses me met maintenant à portée de demontrer. Je n'ai besoin d'aucune
hypothèse ni d'aucune supposition pour cela: j'en atteste tous les
naturalistes observateurs."
3. In a remarkable essay [Footnote: "Entwurf einer Darstellung der zwischen
dem Embryozustände der höheren Thiere und dem permanenten der niederen
stattfindenden Parallele," _Beyträge zur Vergleichenden Anatomie_, Bd.
ii. 1811.] Meckel remarks--
"There is no good physiologist who has not been struck by the observation
that the original form of all organisms is one and the same, and that out
of this one form, all, the lowest as well as the highest, are developed in
such a manner that the latter pass through the permanent forms of the
former as transitory stages. Aristotle, Haller, Harvey, Kielmeyer,
Autenrieth, and many others, have either made this observation
incidentally, or, especially the latter, have drawn particular attention to
it, and deduced therefrom results of permanent importance for physiology."
Meckel proceeds to exemplify the thesis, that the lower forms of animals
represent stages in the course of the development of the higher, with a
large series of illustrations.
After comparing the Salamanders and the perennibranchiate _Urodela_
with the Tadpoles and the Frogs, and enunciating the law that the more
highly any animal is organised the more quickly does it pass through the
lower stages, Meckel goes on to say--
"From these lowest Vertebrata to the highest, and to the highest forms
among these, the comparison between the embryonic conditions of the higher
animals and the adult states of the lower can be more completely and
thoroughly instituted than if the survey is extended to the Invertebrata,
inasmuch as the latter are in many respects constructed upon an altogether
too dissimilar type; indeed they often differ from one another far more
than the lowest vertebrate does from the highest mammal; yet the following
pages will show that the comparison may also be extended to them with
interest. In fact, there is a period when, as Aristotle long ago said, the
embryo of the highest animal has the form of a mere worm; and, devoid of
internal and external organisation, is merely an almost structureless lump
of polype substance. Notwithstanding the origin of organs, it still for a
certain time, by reason of its want of an internal bony skeleton, remains
worm and mollusk, and only later enters into the series of the Vertebrata,
although traces of the vertebral column even in the earliest periods
testify its claim to a place in that series."--_Op, cit_ pp. 4, 5.
If Meckel's proposition is so far qualified, that the comparison of adult
with embryonic forms is restricted within the limits of one type of
organisation; and, if it is further recollected that the resemblance
between the permanent lower form and the embryonic stage of a higher form
is not special but general, it is in entire accordance with modern
embryology; although there is no branch of biology which has grown so
largely, and improved its methods so much, since Meckel's time, as this. In
its original form, the doctrine of "arrest of development," as advocated by
Geoffroy Saint-Hilaire and Serres, was no doubt an overstatement of the
case. It is not true, for example, that a fish is a reptile arrested in its
development, or that a reptile was ever a fish: but it is true that the
reptile embryo, at one stage of its development, is an organism which, if
it had an independent existence, must be classified among fishes; and all
the organs of the reptile pass, in the course of their development, through
conditions which are closely analogous to those which are permanent in some
fishes.
4. That branch of biology which is termed Morphology is a commentary upon,
and expansion of, the proposition that widely different animals or plants,
and widely different parts of animals or plants, are constructed upon the
same plan. From the rough comparison of the skeleton of a bird with that of
a man by Belon, in the sixteenth century (to go no farther back), down to
the theory of the limbs and the theory of the skull at the present day; or,
from the first demonstration of the homologies of the parts of a flower by
C. F. Wolff, to the present elaborate analysis of the floral organs,
morphology exhibits a continual advance towards the demonstration of a
fundamental unity among the seeming diversities of living structures. And
this demonstration has been completed by the final establishment of the
cell theory, which involves the admission of a primitive conformity, not
only of all the elementary structures in animals and plants respectively,
but of those in the one of these great divisions of living things with
those in the other. No _à priori_ difficulty can be said to stand in
the way of evolution, when it can be shown that all animals and all plants
proceed by modes of development, which are similar in principle, from a
fundamental protoplasmic material.
5. The innumerable cases of structures, which are rudimentary and
apparently useless, in species, the close allies of which possess
well-developed and functionally important homologous structures, are
readily intelligible on the theory of evolution, while it is hard to
conceive their _raison d'être_ on any other hypothesis. However, a
cautious reasoner will probably rather explain such cases deductively from
the doctrine of evolution than endeavour to support the doctrine of
evolution by them. For it is almost impossible to prove that any structure,
however rudimentary, is useless--that is to say, that it plays no part
whatever in the economy; and, if it is in the slightest degree useful,
there is no reason why, on the hypothesis of direct creation, it should not
have been created. Nevertheless, double-edged as is the argument from
rudimentary organs, there is probably none which has produced a greater
effect in promoting the general acceptance of the theory of evolution.
6. The older advocates of evolution sought for the causes of the process
exclusively in the influence of varying conditions, such as climate and
station, or hybridisation, upon living forms. Even Treviranus has got no
farther than this point. Lamarck introduced the conception of the action of
an animal on itself as a factor in producing modification. Starting from
the well-known fact that the habitual use of a limb tends to develop the
muscles of the limb, and to produce a greater and greater facility in using
it, he made the general assumption that the effort of an animal to exert an
organ in a given direction tends to develop the organ in that direction.
But a little consideration showed that, though Lamarck had seized what, as
far it goes, is a true cause of modification, it is a cause the actual
effects of which are wholly inadequate to account for any considerable
modification in animals, and which can have no influence at all in the
vegetable world; and probably nothing contributed so much to discredit
evolution, in the early part of this century, as the floods of easy
ridicule which were poured upon this part of Lamarck's speculation. The
theory of natural selection, or survival of the fittest, was suggested by
Wells in 1813, and further elaborated by Matthew in 1831. But the pregnant
suggestions of these writers remained practically unnoticed and forgotten,
until the theory was independently devised and promulgated by Darwin and
Wallace in 1858, and the effect of its publication was immediate and
profound.
Those who were unwilling to accept evolution, without better grounds than
such as are offered by Lamarck, or the author of that particularly
unsatisfactory book, the "Vestiges of the Natural History of the Creation,"
and who therefore preferred to suspend their judgment on the question,
found in the principle of selective breeding, pursued in all its
applications with marvellous knowledge and skill by Mr. Darwin, a valid
explanation of the occurrence of varieties and races; and they saw clearly
that, if the explanation would apply to species, it would not only solve
the problem of their evolution, but that it would account for the facts of
teleology, as well as for those of morphology; and for the persistence of
some forms of life unchanged through long epochs of time, while others
undergo comparatively rapid metamorphosis.
How far "natural selection" suffices for the production of species remains
to be seen. Few can doubt that, if not the whole cause, it is a very
important factor in that operation; and that it must play a great part in
the sorting out of varieties into those which are transitory and those
which are permanent.
But the causes and conditions of variation have yet to be thoroughly
explored; and the importance of natural selection will not be impaired,
even if further inquiries should prove that variability is definite, and is
determined in certain directions rather than in others, by conditions
inherent in that which varies. It is quite conceivable that every species
tends to produce varieties of a limited number and kind, and that the
effect of natural selection is to favour the development of some of these,
while it opposes the development of others along their predetermined lines
of modification.
7. No truths brought to light by biological investigation were better
calculated to inspire distrust of the dogmas intruded upon science in the
name of theology, than those which relate to the distribution of animals
and plants on the surface of the earth. Very skilful accommodation was
needful, if the limitation of sloths to South America, and of the
ornithorhynchus to Australia, was to be reconciled with the literal
interpretation of the history of the deluge; and with the establishment of
the existence of distinct provinces of distribution, any serious belief in
the peopling of the world by migration from Mount Ararat came to an end.
Under these circumstances, only one alternative was left for those who
denied the occurrence of evolution--namely, the supposition that the
characteristic animals and plants of each great province were created as
such, within the limits in which we find them. And as the hypothesis of
"specific centres," thus formulated, was heterodox from the theological
point of view, and unintelligible under its scientific aspect, it may be
passed over without further notice, as a phase of transition from the
creational to the evolutional hypothesis.
8. In fact, the strongest and most conclusive arguments in favour of
evolution are those which are based upon the facts of geographical, taken
in conjunction with those of geological, distribution.
Both Mr. Darwin and Mr. Wallace lay great stress on the close relation
which obtains between the existing fauna of any region and that of the
immediately antecedent geological epoch in the same region; and rightly,
for it is in truth inconceivable that there should be no genetic connection
between the two. It is possible to put into words the proposition that all
the animals and plants of each geological epoch were annihilated and that a
new set of very similar forms was created for the next epoch; but it may be
doubted if any one who ever tried to form a distinct mental image of this
process of spontaneous generation on the grandest scale, ever really
succeeded in realising it.
Within the last twenty years, the attention of the best palæontologists has
been withdrawn from the hodman's work of making "new species" of fossils,
to the scientific task of completing our knowledge of individual species,
and tracing out the succession of the forms presented by any given type in
time.
Those who desire to inform themselves of the nature and extent of the
evidence bearing on these questions may consult the works of Rütimeyer,
Gaudry, Kowalewsky, Marsh, and the writer of the present article. It must
suffice, in this place, to say that the successive forms of the Equine type
have been fully worked out; while those of nearly all the other existing
types of Ungulate mammals and of the _Carnivora_ have been almost as
closely followed through the Tertiary deposits; the gradations between
birds and reptiles have been traced; and the modifications undergone by the
_Crocodilia_, from the Triassic epoch to the present day, have been
demonstrated. On the evidence of palæontology, the evolution of many
existing forms of animal life from their predecessors is no longer an
hypothesis, but an historical fact; it is only the nature of the
physiological factors to which that evolution is due which is still open to
discussion.
[At page 209, the reference to Erasmus Darwin does not do justice to that
ingenious writer, who, in the 39th section of the _Zoonomia_, clearly
and repeatedly enunciates the theory of the inheritance of acquired
modifications. For example "From their first rudiment, or primordium, to
the termination of their lives, all animals undergo perpetual
transformations; which are in part produced by their own exertions in
consequence of their desires and aversions, of their pleasures and their
pains, or of irritation, or of associations; and many of these acquired
forms or propensities are transmitted to their posterity." _Zoonomia_
I., p. 506. 1893.]
VII
THE COMING OF AGE OF "THE ORIGIN OF SPECIES"
[1880]
Many of you will be familiar with the aspect of this small green-covered
book. It is a copy of the first edition of the "Origin of Species," and
bears the date of its production--the 1st of October 1859. Only a few
months, therefore, are needed to complete the full tale of twenty-one years
since its birthday.
Those whose memories carry them back to this time will remember that the
infant was remarkably lively, and that a great number of excellent persons
mistook its manifestations of a vigorous individuality for mere
naughtiness; in fact there was a very pretty turmoil about its cradle. My
recollections of the period are particularly vivid, for, having conceived a
tender affection for a child of what appeared to me to be such remarkable
promise, I acted for some time in the capacity of a sort of under-nurse,
and thus came in for my share of the storms which threatened the very life
of the young creature. For some years it was undoubtedly warm work; but
considering how exceedingly unpleasant the apparition of the newcomer must
have been to those who did not fall in love with him at first sight, I
think it is to the credit of our age that the war was not fiercer, and that
the more bitter and unscrupulous forms of opposition died away as soon as
they did.
I speak of this period as of something past and gone, possessing merely an
historical, I had almost said an antiquarian interest. For, during the
second decade of the existence of the "Origin of Species," opposition,
though by no means dead, assumed a different aspect. On the part of all
those who had any reason to respect themselves, it assumed a thoroughly
respectful character. By this time, the dullest began to perceive that the
child was not likely to perish of any congenital weakness or infantile
disorder, but was growing into a stalwart personage, upon whom mere goody
scoldings and threatenings with the birch-rod were quite thrown away.
In fact, those who have watched the progress of science within the last ten
years will bear me out to the full, when I assert that there is no field of
biological inquiry in which the influence of the "Origin of Species" is not
traceable; the foremost men of science in every country are either avowed
champions of its leading doctrines, or at any rate abstain from opposing
them; a host of young and ardent investigators seek for and find
inspiration and guidance in Mr. Darwin's great work; and the general
doctrine of evolution, to one side of which it gives expression, obtains,
in the phenomena of biology, a firm base of operations whence it may
conduct its conquest of the whole realm of Nature.
History warns us, however, that it is the customary fate of new truths to
begin as heresies and to end as superstitions; and, as matters now stand,
it is hardly rash to anticipate that, in another twenty years, the new
generation, educated under the influences of the present day, will be in
danger of accepting the main doctrines of the "Origin of Species," with as
little reflection, and it may be with as little justification, as so many
of our contemporaries, twenty years ago, rejected them.
Against any such a consummation let us all devoutly pray; for the
scientific spirit is of more value than its products, and irrationally held
truths may be more harmful than reasoned errors. Now the essence of the
scientific spirit is criticism. It tells us that whenever a doctrine claims
our assent we should reply, Take it if you can compel it. The struggle for
existence holds as much in the intellectual as in the physical world. A
theory is a species of thinking, and its right to exist is coextensive with
its power of resisting extinction by its rivals.
From this point of view, it appears to me that it would be but a poor way
of celebrating the Coming of Age of the "Origin of Species," were I merely
to dwell upon the facts, undoubted and remarkable as they are, of its
far-reaching influence and of the great following of ardent disciples who
are occupied in spreading and developing its doctrines. Mere insanities and
inanities have before now swollen to portentous size in the course of
twenty years. Let us rather ask this prodigious change in opinion to
justify itself: let us inquire whether anything has happened since 1859,
which will explain, on rational grounds, why so many are worshipping that
which they burned, and burning that which they worshipped. It is only in
this way that we shall acquire the means of judging whether the movement we
have witnessed is a mere eddy of fashion, or truly one with the
irreversible current of intellectual progress, and, like it, safe from
retrogressive reaction.
Every belief is the product of two factors: the first is the state of the
mind to which the evidence in favour of that belief is presented; and the
second is the logical cogency of the evidence itself. In both these
respects, the history of biological science during the last twenty years
appears to me to afford an ample explanation of the change which has taken
place; and a brief consideration of the salient events of that history will
enable us to understand why, if the "Origin of Species" appeared now, it
would meet with a very different reception from that which greeted it in
1859.
One-and-twenty years ago, in spite of the work commenced by Hutton and
continued with rare skill and patience by Lyell, the dominant view of the
past history of the earth was catastrophic. Great and sudden physical
revolutions, wholesale creations and extinctions of living beings, were the
ordinary machinery of the geological epic brought into fashion by the
misapplied genius of Cuvier. It was gravely maintained and taught that the
end of every geological epoch was signalised by a cataclysm, by which every
living being on the globe was swept away, to be replaced by a brand-new
creation when the world returned to quiescence. A scheme of nature which
appeared to be modelled on the likeness of a succession of rubbers of
whist, at the end of each of which the players upset the table and called
for a new pack, did not seem to shock anybody.
I may be wrong, but I doubt if, at the present time, there is a single
responsible representative of these opinions left. The progress of
scientific geology has elevated the fundamental principle of
uniformitarianism, that the explanation of the past is to be sought in the
study of the present, into the position of an axiom; and the wild
speculations of the catastrophists, to which we all listened with respect a
quarter of a century ago, would hardly find a single patient hearer at the
present day. No physical geologist now dreams of seeking, outside the range
of known natural causes, for the explanation of anything that happened
millions of years ago, any more than he would be guilty of the like
absurdity in regard to current events.
The effect of this change of opinion upon biological speculation is
obvious. For, if there have been no periodical general physical
catastrophes, what brought about the assumed general extinctions and
re-creations of life which are the corresponding biological catastrophes?
And, if no such interruptions of the ordinary course of nature have taken
place in the organic, any more than in the inorganic, world, what
alternative is there to the admission of evolution?
The doctrine of evolution in biology is the necessary result of the logical
application of the principles of uniformitarianism to the phenomena of
life. Darwin is the natural successor of Hutton and Lyell, and the "Origin
of Species" the logical sequence of the "Principles of Geology."
The fundamental doctrine of the "Origin of Species," as of all forms of the
theory of evolution applied to biology, is "that the innumerable species,
genera, and families of organic beings with which the world is peopled have
all descended, each within its own class or group, from common parents, and
have all been modified in the course of descent." [Footnote: _Origin of
Species_, ed. I, p. 457.]
And, in view of the facts of geology, it follows that all living animals
and plants "are the lineal descendants of those which lived long before the
Silurian epoch." [Footnote: _Origin of Species_, p. 458.]
It is an obvious consequence of this theory of descent with modification,
as it is sometimes called, that all plants and animals, however different
they may now be, must, at one time or other, have been connected by direct
or indirect intermediate gradations, and that the appearance of isolation
presented by various groups of organic beings must be unreal.
No part of Mr. Darwin's work ran more directly counter to the
prepossessions of naturalists twenty years ago than this. And such
prepossessions were very excusable, for there was undoubtedly a great deal
to be said, at that time, in favour of the fixity of species and of the
existence of great breaks, which there was no obvious or probable means of
filling up, between various groups of organic beings.
For various reasons, scientific and unscientific, much had been made of the
hiatus between man and the rest of the higher mammalia, and it is no wonder
that issue was first joined on this part of the controversy. I have no wish
to revive past and happily forgotten controversies; but I must state the
simple fact that the distinctions in the cerebral and other characters,
which were so hotly affirmed to separate man from all other animals in
1860, have all been demonstrated to be non-existent, and that the contrary
doctrine is now universally accepted and taught.
But there were other cases in which the wide structural gaps asserted to
exist between one group of animals and another were by no means fictitious;
and, when such structural breaks were real, Mr. Darwin could account for
them only by supposing that the intermediate forms which once existed had
become extinct. In a remarkable passage he says--
"We may thus account even for the distinctness of whole classes from each
other--for instance, of birds from all other vertebrate animals--by the
belief that many animal forms of life have been utterly lost, through which
the early progenitors of birds were formerly connected with the early
progenitors of the other vertebrate classes." [Footnote: _Origin of
Species_, p. 431.] Adverse criticism made merry over such suggestions as
these. Of course it was easy to get out of the difficulty by supposing
extinction; but where was the slightest evidence that such intermediate
forms between birds and reptiles as the hypothesis required ever existed?
And then probably followed a tirade upon this terrible forsaking of the
paths of "Baconian induction."
But the progress of knowledge has justified Mr. Darwin to an extent which
could hardly have been anticipated. In 1862, the specimen of
_Archæopteryx_, which, until the last two or three years, has remained
unique, was discovered; and it is an animal which, in its feathers and the
greater part of its organisation, is a veritable bird, while, in other
parts, it is as distinctly reptilian.
In 1868, I had the honour of bringing under your notice, in this theatre,
the results of investigations made, up to that time, into the anatomical
characters of certain ancient reptiles, which showed the nature of the
modifications in virtue of which the type of the quadrupedal reptile passed
into that of a bipedal bird; and abundant confirmatory evidence of the
justice of the conclusions which I then laid before you has since come to
light.
In 1875, the discovery of the toothed birds of the cretaceous formation in
North America by Professor Marsh completed the series of transitional forms
between birds and reptiles, and removed Mr. Darwin's proposition that "many
animal forms of life have been utterly lost, through which the early
progenitors of birds were formerly connected with the early progenitors of
the other vertebrate classes," from the region of hypothesis to that of
demonstrable fact.
In 1859, there appeared to be a very sharp and clear hiatus between
vertebrated and invertebrated animals, not only in their structure, but,
what was more important, in their development. I do not think that we even
yet know the precise links of connection between the two; but the
investigations of Kowalewsky and others upon the development of
_Amphioxus_ and of the _Tunicata_ prove, beyond a doubt, that the
differences which were supposed to constitute a barrier between the two are
non-existent. There is no longer any difficulty in understanding how the
vertebrate type may have arisen from the invertebrate, though the full
proof of the manner in which the transition was actually effected may still
be lacking.
Again, in 1859, there appeared to be a no less sharp separation between the
two great groups of flowering and flowerless plants. It is only
subsequently that the series of remarkable investigations inaugurated by
Hofmeister has brought to light the extraordinary and altogether unexpected
modifications of the reproductive apparatus in the _Lycopodiaceæ_, the
_Rhizocarpeæ_, and the _Gymnospermeæ_, by which the ferns and the
mosses are gradually connected with the Phanerogamic division of the
vegetable world.
So, again, it is only since 1859 that we have acquired that wealth of
knowledge of the lowest forms of life which demonstrates the futility of
any attempt to separate the lowest plants from the lowest animals, and
shows that the two kingdoms of living nature have a common borderland which
belongs to both, or to neither.
Thus it will be observed that the whole tendency of biological
investigation, since 1859, has been in the direction of removing the
difficulties which the apparent breaks in the series created at that time;
and the recognition of gradation is the first step towards the acceptance
of evolution.
As another great factor in bringing about the change of opinion which has
taken place among naturalists, I count the astonishing progress which has
been made in the study of embryology. Twenty years ago, not only were we
devoid of any accurate knowledge of the mode of development of many groups
of animals and plants, but the methods of investigation were rude and
imperfect. At the present time, there is no important group of organic
beings the development of which has not been carefully studied; and the
modern methods of hardening and section-making enable the embryologist to
determine the nature of the process, in each case, with a degree of
minuteness and accuracy which is truly astonishing to those whose memories
carry them back to the beginnings of modern histology. And the results of
these embryological investigations are in complete harmony with the
requirements of the doctrine of evolution. The first beginnings of all the
higher forms of animal life are similar, and however diverse their adult
conditions, they start from a common foundation. Moreover, the process of
development of the animal or the plant from its primary egg, or germ, is a
true process of evolution--a progress from almost formless to more or less
highly organised matter, in virtue of the properties inherent in that
matter.
To those who are familiar with the process of development, all _a
priori_ objections to the doctrine of biological evolution appear
childish. Any one who has watched the gradual formation of a complicated
animal from the protoplasmic mass, which constitutes the essential element
of a frog's or a hen's egg, has had under his eyes sufficient evidence that
a similar evolution of the whole animal world from the like foundation is,
at any rate, possible.
Yet another product of investigation has largely contributed to the removal
of the objections to the doctrine of evolution current in 1859. It is the
proof afforded by successive discoveries that Mr. Darwin did not
over-estimate the imperfection of the geological record. No more striking
illustration of this is needed than a comparison of our knowledge of the
mammalian fauna of the Tertiary epoch in 1859 with its present condition.
M. Gaudry's researches on the fossils of Pikermi were published in 1868,
those of Messrs. Leidy, Marsh, and Cope, on the fossils of the Western
Territories of America, have appeared almost wholly since 1870, those of M.
Filhol on the phosphorites of Quercy in 1878. The general effect of these
investigations has been to introduce to us a multitude of extinct animals,
the existence of which was previously hardly suspected; just as if
zoologists were to become acquainted with a country, hitherto unknown, as
rich in novel forms of life as Brazil or South Africa once were to
Europeans. Indeed, the fossil fauna of the Western Territories of America
bid fair to exceed in interest and importance all other known Tertiary
deposits put together; and yet, with the exception of the case of the
American tertiaries, these investigations have extended over very limited
areas; and, at Pikermi, were confined to an extremely small space.
Such appear to me to be the chief events in the history of the progress of
knowledge during the last twenty years, which account for the changed
feeling with which the doctrine of evolution is at present regarded by
those who have followed the advance of biological science, in respect of
those problems which bear indirectly upon that doctrine.
But all this remains mere secondary evidence. It may remove dissent, but it
does not compel assent. Primary and direct evidence in favour of evolution
can be furnished only by palæontology. The geological record, so soon as it
approaches completeness, must, when properly questioned, yield either an
affirmative or a negative answer: if evolution has taken place, there will
its mark be left; if it has not taken place, there will lie its refutation.
What was the state of matters in 1859? Let us hear Mr. Darwin, who may be
trusted always to state the case against himself as strongly as possible.
"On this doctrine of the extermination of an infinitude of connecting links
between the living and extinct inhabitants of the world, and at each
successive period between the extinct and still older species, why is not
every geological formation charged with such links? Why does not every
collection of fossil remains afford plain evidence of the gradation and
mutation of the forms of life? We meet with no such evidence, and this is
the most obvious and plausible of the many objections which may be urged
against my theory." [Footnote: _Origin of Species_, ed. 1, p. 463.]
Nothing could have been more useful to the opposition than this
characteristically candid avowal, twisted as it immediately was into an
admission that the writer's views were contradicted by the facts of
palæontology. But, in fact, Mr. Darwin made no such admission. What he says
in effect is, not that palæontological evidence is against him, but that it
is not distinctly in his favour; and, without attempting to attenuate the
fact, he accounts for it by the scantiness and the imperfection of that
evidence.
What is the state of the case now, when, as we have seen, the amount of our
knowledge respecting the mammalia of the Tertiary epoch is increased
fifty-fold, and in some directions even approaches completeness?
Simply this, that, if the doctrine of evolution had not existed,
palaeontologists must have invented it, so irresistibly is it forced upon
the mind by the study of the remains of the Tertiary mammalia which have
been brought to light since 1859.
Among the fossils of Pikermi, Gaudry found the successive stages by which
the ancient civets passed into the more modern hyænas; through the Tertiary
deposits of Western America, Marsh tracked the successive forms by which
the ancient stock of the horse has passed into its present form; and
innumerable less complete indications of the mode of evolution of other
groups of the higher mammalia have been obtained. In the remarkable memoir
on the phosphorites of Quercy, to which I have referred, M. Filhol
describes no fewer than seventeen varieties of the genus _Cynodictis_,
which fill up all the interval between the viverine animals and the
bear-like dog _Amphicyon_; nor do I know any solid ground of objection
to the supposition that, in this _Cynodictis-Amphicyon_ group, we have
the stock whence all the Viveridæ, Felidæ, Hyænidæ, Canidæ, and perhaps the
Procyonidæ and Ursidæ, of the present fauna have been evolved. On the
contrary, there is a great deal to be said in favour.
In the course of summing up his results, M. Filhol observes:--
"During the epoch of the phosphorites, great changes took place in animal
forms, and almost the same types as those which now exist became defined
from one another.
"Under the influence of natural conditions of which we have no exact
knowledge, though traces of them are discoverable, species have been
modified in a thousand ways: races have arisen which, becoming fixed, have
thus produced a corresponding number of secondary species."
In 1859, language of which this is an unintentional paraphrase, occurring
in the "Origin of Species," was scouted as wild speculation; at present, it
is a sober statement of the conclusions to which an acute and
critically-minded investigator is led by large and patient study of the
facts of palæontology. I venture to repeat what I have said before, that so
far as the animal world is concerned, evolution is no longer a speculation,
but a statement of historical fact. It takes its place alongside of those
accepted truths which must be reckoned with by philosophers of all schools.
Thus when, on the first day of October next, "The Origin of Species" comes
of age, the promise of its youth will be amply fulfilled; and we shall be
prepared to congratulate the venerated author of the book, not only that
the greatness of his achievement and its enduring influence upon the
progress of knowledge have won him a place beside our Harvey; but, still
more, that, like Harvey, he has lived long enough to outlast detraction and
opposition, and to see the stone that the builders rejected become the
head-stone of the corner.
VIII
CHARLES DARWIN
[_Nature_, April 27th, 1882]
Very few, even among those who have taken the keenest interest in the
progress of the revolution in natural knowledge set afoot by the
publication of "The Origin of Species," and who have watched, not without
astonishment, the rapid and complete change which has been effected both
inside and outside the boundaries of the scientific world in the attitude
of men's minds towards the doctrines which are expounded in that great
work, can have been prepared for the extraordinary manifestation of
affectionate regard for the man, and of profound reverence for the
philosopher, which followed the announcement, on Thursday last, of the
death of Mr. Darwin.
Not only in these islands, where so many have felt the fascination of
personal contact with an intellect which had no superior, and with a
character which was even nobler than the intellect; but, in all parts of
the civilised world, it would seem that those whose business it is to feel
the pulse of nations and to know what interests the masses of mankind, were
well aware that thousands of their readers would think the world the poorer
for Darwin's death, and would dwell with eager interest upon every incident
of his history. In France, in Germany, in Austro-Hungary, in Italy, in the
United States, writers of all shades of opinion, for once unanimous, have
paid a willing tribute to the worth of our great countryman, ignored in
life by the official representatives of the kingdom, but laid in death
among his peers in Westminster Abbey by the will of the intelligence of the
nation.
It is not for us to allude to the sacred sorrows of the bereaved home at
Down; but it is no secret that, outside that domestic group, there are many
to whom Mr. Darwin's death is a wholly irreparable loss. And this not
merely because of his wonderfully genial, simple, and generous nature; his
cheerful and animated conversation, and the infinite variety and accuracy
of his information; but because the more one knew of him, the more he
seemed the incorporated ideal of a man of science. Acute as were his
reasoning powers, vast as was his knowledge, marvellous as was his
tenacious industry, under physical difficulties which would have converted
nine men out of ten into aimless invalids; it was not these qualities,
great as they were, which impressed those who were admitted to his intimacy
with involuntary veneration, but a certain intense and almost passionate
honesty by which all his thoughts and actions were irradiated, as by a
central fire.
It was this rarest and greatest of endowments which kept his vivid
imagination and great speculative powers within due bounds; which compelled
him to undertake the prodigious labours of original investigation and of
reading, upon which his published works are based; which made him accept
criticisms and suggestions from anybody and everybody, not only without
impatience, but with expressions of gratitude sometimes almost comically in
excess of their value; which led him to allow neither himself nor others to
be deceived by phrases, and to spare neither time nor pains in order to
obtain clear and distinct ideas upon every topic with which he occupied
himself.
One could not converse with Darwin without being reminded of Socrates.
There was the same desire to find some one wiser than himself; the same
belief in the sovereignty of reason; the same ready humour; the same
sympathetic interest in all the ways and works of men. But instead of
turning away from the problems of Nature as hopelessly insoluble, our
modern philosopher devoted his whole life to attacking them in the spirit
of Heraclitus and of Democritus, with results which are the substance of
which their speculations were anticipatory shadows.
The due appreciation, or even enumeration, of these results is neither
practicable nor desirable at this moment. There is a time for all things--a
time for glorying in our ever-extending conquests over the realm of Nature,
and a time for mourning over the heroes who have led us to victory.
None have fought better, and none have been more fortunate, than Charles
Darwin. He found a great truth trodden underfoot, reviled by bigots, and
ridiculed by all the world; he lived long enough to see it, chiefly by his
own efforts, irrefragably established in science, inseparably incorporated
with the common thoughts of men, and only hated and feared by those who
would revile, but dare not. What shall a man desire more than this? Once
more the image of Socrates rises unbidden, and the noble peroration of the
"Apology" rings in our ears as if it were Charles Darwin's farewell:--
"The hour of departure has arrived, and we go our ways--I to die and you to
live. Which is the better, God only knows."
IX
THE DARWIN MEMORIAL
[June 9th, 1885]
_Address by the President of the Royal Society, in the name of the
Memorial Committee, on handing over the statue of Darwin to H.R.H. the
Prince of Wales, as representative of the Trustees of the British
Museum_.
YOUR ROYAL HIGHNESS,--It is now three years since the announcement of the
death of our famous countryman, Charles Darwin, gave rise to a
manifestation of public feeling, not only in these realms, but throughout
the civilised world, which, if I mistake not, is without precedent in the
modest annals of scientific biography.
The causes of this deep and wide outburst of emotion are not far to seek.
We had lost one of these rare ministers and interpreters of Nature whose
names mark epochs in the advance of natural knowledge. For, whatever be the
ultimate verdict of posterity upon this or that opinion which Mr. Darwin
has propounded; whatever adumbrations or anticipations of his doctrines may
be found in the writings of his predecessors; the broad fact remains that,
since the publication and by reason of the publication, of "The Origin of
Species" the fundamental conceptions and the aims of the students of living
Nature have been completely changed. From that work has sprung a great
renewal, a true "instauratio magna" of the zoological and botanical
sciences.
But the impulse thus given to scientific thought rapidly spread beyond the
ordinarily recognised limits of biology. Psychology, Ethics, Cosmology were
stirred to their foundations, and the "Origin of Species" proved itself to
be the fixed point which the general doctrine of evolution needed in order
to move the world. "Darwinism," in one form or another, sometimes strangely
distorted and mutilated, became an everyday topic of men's speech, the
object of an abundance both of vituperation and of praise, more often than
of serious study.
It is curious now to remember how largely, at first, the objectors
predominated; but considering the usual fate of new views, it is still more
curious to consider for how short a time the phase of vehement opposition
lasted. Before twenty years had passed, not only had the importance of Mr.
Darwin's work been fully recognised, but the world had discerned the
simple, earnest, generous character of the man, that shone through every
page of his writings.
I imagine that reflections such as these swept through the minds alike of
loving friends and of honourable antagonists when Mr. Darwin died; and that
they were at one in the desire to honour the memory of the man who, without
fear and without reproach, had successfully fought the hardest intellectual
battle of these days.
It was in satisfaction of these just and generous impulses that our great
naturalist's remains were deposited in Westminster Abbey; and that,
immediately afterwards, a public meeting, presided over by my lamented
predecessor, Mr. Spottiswoode, was held in the rooms of the Royal Society,
for the purpose of considering what further step should be taken towards
the same end.
It was resolved to invite subscriptions, with the view of erecting a statue
of Mr. Darwin in some suitable locality; and to devote any surplus to the
advancement of the biological sciences.
Contributions at once flowed in from Austria, Belgium, Brazil, Denmark,
France, Germany, Holland, Italy, Norway, Portugal, Russia, Spain, Sweden,
Switzerland, the United States, and the British Colonies, no less than from
all parts of the three kingdoms; and they came from all classes of the
community. To mention one interesting case, Sweden sent in 2296
subscriptions "from all sorts of people," as the distinguished man of
science who transmitted them wrote, "from the bishop to the seamstress, and
in sums from five pounds to two pence."
The Executive Committee has thus been enabled to carry out the objects
proposed. A "Darwin Fund" has been created, which is to be held in trust by
the Royal Society, and is to be employed in the promotion of biological
research.
The execution of the statue was entrusted to Mr. Boehm; and I think that
those who had the good fortune to know Mr. Darwin personally will admire
the power of artistic divination which has enabled the sculptor to place
before us so very characteristic a likeness of one whom he had not seen.
It appeared to the Committee that, whether they regarded Mr. Darwin's
career or the requirements of a work of art, no site could be so
appropriate as this great hall, and they applied to the Trustees of the
British Museum for permission to erect it in its present position.
That permission was most cordially granted, and I am desired to tender the
best thanks of the Committee to the Trustees for their willingness to
accede to our wishes.
I also beg leave to offer the expression of our gratitude to your Royal
Highness for kindly consenting to represent the Trustees to-day. It only
remains for me, your Royal Highness, my Lords and Gentlemen, Trustees of
the British Museum, in the name of the Darwin Memorial Committee, to
request you to accept this statue of Charles Darwin.
We do not make this request for the mere sake of perpetuating a memory; for
so long as men occupy themselves with the pursuit of truth, the name of
Darwin runs no more risk of oblivion than does that of Copernicus, or that
of Harvey.
Nor, most assuredly, do we ask you to preserve the statue in its cynosural
position in this entrance-hall of our National Museum of Natural History as
evidence that Mr. Darwin's views have received your official sanction; for
science does not recognise such sanctions, and commits suicide when it
adopts a creed.
No; we beg you to cherish this Memorial as a symbol by which, as generation
after generation of students of Nature enter yonder door, they shall be
reminded of the ideal according to which they must shape their lives, if
they would turn to the best account the opportunities offered by the great
institution under your charge.
X
OBITUARY [Footnote: From the Obituary Notices of the _Proceedings of the
Royal Society_, vol. 44.]
[1888]
Charles Robert Darwin was the fifth child and second son of Robert Waring
Darwin and Susannah Wedgwood, and was born on the 12th February, 1809, at
Shrewsbury, where his father was a physician in large practice.
Mrs. Robert Darwin died when her son Charles was only eight years old, and
he hardly remembered her. A daughter of the famous Josiah Wedgwood, who
created a new branch of the potter's art, and established the great works
of Etruria, could hardly fail to transmit important mental and moral
qualities to her children; and there is a solitary record of her direct
influence in the story told by a schoolfellow, who remembers Charles Darwin
"bringing a flower to school, and saying that his mother had taught him
how, by looking at the inside of the blossom, the name of the plant could
be discovered." (I., p. 28. [Footnote: The references throughout this
notice are to the _Life and Letters_, unless the contrary is expressly
stated.])
The theory that men of genius derive their qualities from their mothers,
however, can hardly derive support from Charles Darwin's case, in the face
of the patent influence of his paternal forefathers. Dr. Darwin, indeed,
though a man of marked individuality of character, a quick and acute
observer, with much practical sagacity, is said not to have had a
scientific mind. But when his son adds that his father "formed a theory for
almost everything that occurred" (I., p. 20), he indicates a highly
probable source for that inability to refrain from forming an hypothesis on
every subject which he confesses to be one of the leading characteristics
of his own mind, some pages further on (I., p. 103). Dr. R. W. Darwin,
again, was the third son of Erasmus Darwin, also a physician of great
repute, who shared the intimacy of Watt and Priestley, and was widely known
as the author of "Zoonomia," and other voluminous poetical and prose works
which had a great vogue in the latter half of the eighteenth century. The
celebrity which they enjoyed was in part due to the attractive style (at
least according to the taste of that day) in which the author's extensive,
though not very profound, acquaintance with natural phenomena was set
forth; but in a still greater degree, probably, to the boldness of the
speculative views, always ingenious and sometimes fantastic, in which he
indulged. The conception of evolution set afoot by De Maillet and others,
in the early part of the century, not only found a vigorous champion in
Erasmus Darwin, but he propounded an hypothesis as to the manner in which
the species of animals and plants have acquired their characters, which is
identical in principle with that subsequently rendered famous by Lamarck.
That Charles Darwin's chief intellectual inheritance came to him from the
paternal side, then, is hardly doubtful. But there is nothing to show that
he was, to any sensible extent, directly influenced by his grandfather's
biological work. He tells us that a perusal of the "Zoonomia" in early life
produced no effect upon him, although he greatly admired it; and that, on
reading it again, ten or fifteen years afterwards, he was much
disappointed, "the proportion of speculation being so large to the facts
given." But with his usual anxious candour he adds, "Nevertheless, it is
probable that the hearing, rather early in life, such views maintained and
praised, may have favoured my upholding them, in a different form, in my
'Origin of Species.'" (I., p. 38.) Erasmus Darwin was in fact an
anticipator of Lamarck, and not of Charles Darwin; there is no trace in his
works of the conceptions by the addition of which his grandson
metamorphosed the theory of evolution as applied to living things and gave
it a new foundation.
Charles Darwin's childhood and youth afforded no intimation that he would
he, or do, anything out of the common run. In fact, the prognostications of
the educational authorities into whose hands he first fell were most
distinctly unfavourable; and they counted the only boy of original genius
who is known to have come under their hands as no better than a dunce. The
history of the educational experiments to which Darwin was subjected is
curious, and not without a moral for the present generation. There were
four of them, and three were failures. Yet it cannot be said that the
materials on which the pedagogic powers operated were other than good. In
his boyhood Darwin was strong, well-grown, and active, taking the keen
delight in field sports and in every description of hard physical exercise
which is natural to an English country-bred lad; and, in respect of things
of the mind, he was neither apathetic, nor idle, nor one-sided. The
"Autobiography" tells us that he "had much zeal for whatever interested"
him, and he was interested in many and very diverse topics. He could work
hard, and liked a complex subject better than an easy one. The "clear
geometrical proofs" of Euclid delighted him. His interest in practical
chemistry, carried out in an extemporised laboratory, in which he was
permitted to assist by his elder brother, kept him late at work, and earned
him the nickname of "gas" among his schoolfellows. And there could have
been no insensibility to literature in one who, as a boy, could sit for
hours reading Shakespeare, Milton, Scott, and Byron; who greatly admired
some of the Odes of Horace; and who, in later years, on board the "Beagle,"
when only one book could be carried on an expedition, chose a volume of
Milton for his companion.
Industry, intellectual interests, the capacity for taking pleasure in
deductive reasoning, in observation, in experiment, no less than in the
highest works of imagination: where these qualities are present any
rational system of education should surely be able to make something of
them. Unfortunately for Darwin, the Shrewsbury Grammar School, though good
of its kind, was an institution of a type universally prevalent in this
country half a century ago, and by no means extinct at the present day. The
education given was "strictly classical," "especial attention" being "paid
to verse-making," while all other subjects, except a little ancient
geography and history, were ignored. Whether, as in some famous English
schools at that date and much later, elementary arithmetic was also left
out of sight does not appear; but the instruction in Euclid which gave
Charles Darwin so much satisfaction was certainly supplied by a private
tutor. That a boy, even in his leisure hours, should permit himself to be
interested in any but book-learning seems to have been regarded as little
better than an outrage by the head master, who thought it his duty to
administer a public rebuke to young Darwin for wasting his time on such a
contemptible subject as chemistry. English composition and literature,
modern languages, modern history, modern geography, appear to have been
considered to be as despicable as chemistry.
For seven long years Darwin got through his appointed tasks; construed
without cribs, learned by rote whatever was demanded, and concocted his
verses in approved schoolboy fashion. And the result, as it appeared to his
mature judgment, was simply negative. "The school as a means of education
to me was simply a blank." (I. p. 32.) On the other hand, the extraneous
chemical exercises, which the head master treated so contumeliously, are
gratefully spoken of as the "best part" of his education while at school.
Such is the judgment of the scholar on the school; as might be expected, it
has its counterpart in the judgment of the school on the scholar. The
collective intelligence of the staff of Shrewsbury School could find
nothing but dull mediocrity in Charles Darwin. The mind that found
satisfaction in knowledge, but very little in mere learning; that could
appreciate literature, but had no particular aptitude for grammatical
exercises; appeared to the "strictly classical" pedagogue to be no mind at
all. As a matter of fact, Darwin's school education left him ignorant of
almost all the things which it would have been well for him to know, and
untrained in all the things it would have been useful for him to be able to
do, in after life. Drawing, practice in English composition, and
instruction in the elements of the physical sciences, would not only have
been infinitely valuable to him in reference to his future career, but
would have furnished the discipline suited to his faculties, whatever that
career might be. And a knowledge of French and German, especially the
latter, would have removed from his path obstacles which he never fully
overcame.
Thus, starved and stunted on the intellectual side, it is not surprising
that Charles Darwin's energies were directed towards athletic amusements
and sport, to such an extent, that even his kind and sagacious father could
be exasperated into telling him that "he cared for nothing but shooting,
dogs, and rat-catching." (I. p. 32.) It would be unfair to expect even the
wisest of fathers to have foreseen that the shooting and the rat-catching,
as training in the ways of quick observation and in physical endurance,
would prove more valuable than the construing and verse-making to his son,
whose attempt, at a later period of his Life, to persuade himself "that
shooting was almost an intellectual employment: it required so much skill
to judge where to find most game, and to hunt the dogs well" (I. p. 43),
was by no means so sophistical as he seems to have been ready to admit.
In 1825, Dr. Darwin came to the very just conclusion that his son Charles
would do no good by remaining at Shrewsbury School, and sent him to join
his elder brother Erasmus, who was studying medicine at Edinburgh, with the
intention that the younger son should also become a medical practitioner.
Both sons, however, were well aware that their inheritance would relieve
them from the urgency of the struggle for existence which most professional
men have to face; and they seemed to have allowed their tastes, rather than
the medical curriculum, to have guided their studies. Erasmus Darwin was
debarred by constant ill-health from seeking the public distinction which
his high intelligence and extensive knowledge would, under ordinary
circumstances, have insured. He took no great interest in biological
subjects, but his companionship must have had its influence on his brother.
Still more was exerted by friends like Coldstream and Grant, both
subsequently well-known zoologists (and the latter an enthusiastic
Lamarckian), by whom Darwin was induced to interest himself in marine
zoology. A notice of the ciliated germs of _Flustra_, communicated to
the Plinian Society in 1826, was the first fruits of Darwin's half century
of scientific work. Occasional attendance at the Wernerian Society brought
him into relation with that excellent ornithologist the elder Macgillivray,
and enabled him to see and hear Audubon. Moreover, he got lessons in
bird-stuffing from a negro, who had accompanied the eccentric traveller
Waterton in his wanderings, before settling in Edinburgh.
No doubt Darwin picked up a great deal of valuable knowledge during his two
years' residence in Scotland; but it is equally clear that next to none of
it came through the regular channels of academic education. Indeed, the
influence of the Edinburgh professoriate appears to have been mainly
negative, and in some cases deterrent; creating in his mind, not only a
very low estimate of the value of lectures, but an antipathy to the
subjects which had been the occasion of the boredom inflicted upon him by
their instrumentality. With the exception of Hope, the Professor of
Chemistry, Darwin found them all "intolerably dull." Forty years afterwards
he writes of the lectures of the Professor of Materia Medica that they were
"fearful to remember." The Professor of Anatomy made his lectures "as dull
as he was himself," and he must have been very dull to have wrung from his
victim the sharpest personal remark recorded as his. But the climax seems
to have been attained by the Professor of Geology and Zoology, whose
prælections were so "incredibly dull" that they produced in their hearer
the somewhat rash determination never "to read a book on geology or in any
way to study the science" so long as he lived. (I. p. 41.)
There is much reason to believe that the lectures in question were
eminently qualified to produce the impression which they made; and there
can be little doubt, that Darwin's conclusion that his time was better
employed in reading than in listening to such lectures was a sound one. But
it was particularly unfortunate that the personal and professorial dulness
of the Professor of Anatomy, combined with Darwin's sensitiveness to the
disagreeable concomitants of anatomical work, drove him away from the
dissecting room. In after life, he justly recognised that this was an
"irremediable evil" in reference to the pursuits he eventually adopted;
indeed, it is marvellous that he succeeded in making up for his lack of
anatomical discipline, so far as his work on the Cirripedes shows he did.
And the neglect of anatomy had the further unfortunate result that it
excluded him from the best opportunity of bringing himself into direct
contact with the facts of nature which the University had to offer. In
those days, almost the only practical scientific work accessible to
students was anatomical, and the only laboratory at their disposal the
dissecting room.
We may now console ourselves with the reflection that the partial evil was
the general good. Darwin had already shown an aptitude for practical
medicine (I. p. 37); and his subsequent career proved that he had the
making of an excellent anatomist. Thus, though his horror of operations
would probably have shut him off from surgery, there was nothing to prevent
him (any more than the same peculiarity prevented his father) from passing
successfully through the medical curriculum and becoming, like his father
and grandfather, a successful physician, in which case "The Origin of
Species" would not have been written. Darwin has jestingly alluded to the
fact that the shape of his nose (to which Captain Fitzroy objected), nearly
prevented his embarkation in the "Beagle"; it may be that the sensitiveness
of that organ secured him for science.
At the end of two years' residence in Edinburgh it hardly needed Dr.
Darwin's sagacity to conclude that a young man, who found nothing but
dulness in professorial lucubrations, could not bring himself to endure a
dissecting room, fled from operations, and did not need a profession as a
means of livelihood, was hardly likely to distinguish himself as a student
of medicine. He therefore made a new suggestion, proposing that his son
should enter an English University and qualify for the ministry of the
Church. Charles Darwin found the proposal agreeable, none the less,
probably, that a good deal of natural history and a little shooting were by
no means held, at that time, to be incompatible with the conscientious
performance of the duties of a country clergyman. But it is characteristic
of the man, that he asked time for consideration, in order that he might
satisfy himself that he could sign the Thirty-nine Articles with a clear
conscience. However, the study of "Pearson on the Creeds" and a few other
books of divinity soon assured him that his religious opinions left nothing
to be desired on the score of orthodoxy, and he acceded to his father's
proposition.
The English University selected was Cambridge; but an unexpected obstacle
arose from the fact that, within the two years which had elapsed, since the
young man who had enjoyed seven years of the benefit of a strictly
classical education had left school, he had forgotten almost everything he
had learned there, "even to some few of the Greek letters." (I. p. 46.)
Three months with a tutor, however, brought him back to the point of
translating Homer and the Greek Testament "with moderate facility," and
Charles Darwin commenced the third educational experiment of which he was
the subject, and was entered on the books of Christ's College in October
1827. So far as the direct results of the academic training thus received
are concerned, the English University was not more successful than the
Scottish. "During the three years which I spent at Cambridge my time was
wasted, as far as the academical studies were concerned, as completely as
at Edinburgh and as at school." (I. p. 46.) And yet, as before, there is
ample evidence that this negative result cannot be put down to any native
defect on the part of the scholar. Idle and dull young men, or even young
men who being neither idle nor dull, are incapable of caring for anything
but some hobby, do not devote themselves to the thorough study of Paley's
"Moral Philosophy," and "Evidences of Christianity"; nor are their
reminiscences of this particular portion of their studies expressed in
terms such as the following: "The logic of this book [the 'Evidences'] and,
as I may add, of his 'Natural Theology' gave me as much delight as did
Euclid." (I. p. 47.)
The collector's instinct, strong in Darwin from his childhood, as is
usually the case in great naturalists, turned itself in the direction of
Insects during his residence at Cambridge. In childhood it had been damped
by the moral scruples of a sister, as to the propriety of catching and
killing insects for the mere sake of possessing them, but now it broke out
afresh, and Darwin became an enthusiastic beetle collector. Oddly enough he
took no scientific interest in beetles, not even troubling himself to make
out their names; his delight lay in the capture of a species which turned
out to be rare or new, and still more in finding his name, as captor,
recorded in print. Evidently, this beetle-hunting hobby had little to do
with science, but was mainly a new phase of the old and undiminished love
of sport. In the intervals of beetle-catching, when shooting and hunting
were not to be had, riding across country answered the purpose. These
tastes naturally threw the young undergraduate among a set of men who
preferred hard riding: to hard reading, and wasted the midnight oil upon
other pursuits than that of academic distinction. A superficial observer
might have had some grounds to fear that Dr. Darwin's wrathful prognosis
might yet be verified. But if the eminently social tendencies of a vigorous
and genial nature sought an outlet among a set of jovial sporting friends,
there were other and no less strong proclivities which brought him into
relation with associates of a very different stamp.
Though almost without ear and with a very defective memory for music,
Darwin was so strongly and pleasurably affected by it that he became a
member of a musical society; and an equal lack of natural capacity for
drawing did not prevent him from studying good works of art with much care.
An acquaintance with even the rudiments of physical science was no part of
the requirements for the ordinary Cambridge degree. But there were
professors both of Geology and of Botany whose lectures were accessible to
those who chose to attend them. The occupants of these chairs, in Darwin's
time, were eminent men and also admirable lecturers in their widely
different styles. The horror of geological lectures which Darwin had
acquired at Edinburgh, unfortunately prevented him from going within reach
of the fervid eloquence of Sedgwick; but he attended the botanical course,
and though he paid no serious attention to the subject, he took great
delight in the country excursions, which Henslow so well knew how to make
both pleasant and instructive. The Botanical Professor was, in fact, a man
of rare character and singularly extensive acquirements in all branches of
natural history. It was his greatest pleasure to place his stores of
knowledge at the disposal of the young men who gathered about him, and who
found in him, not merely an encyclopedic teacher but a wise counsellor,
and, in case of worthiness, a warm friend. Darwin's acquaintance with him
soon ripened into a friendship which was terminated only by Henslow's death
in 1861, when his quondam pupil gave touching expression to his sense of
what he owed to one whom he calls (in one of his letters) his "dear old
master in Natural History." (II. p. 217.) It was by Henslow's advice that
Darwin was led to break the vow he had registered against making an
acquaintance with geology; and it was through Henslow's good offices with
Sedgwick that he obtained the opportunity of accompanying the Geological
Professor on one of his excursions in Wales. He then received a certain
amount of practical instruction in Geology, the value of which he
subsequently warmly acknowledged. (I. p. 237.) In another direction,
Henslow did him an immense, though not altogether intentional service, by
recommending him to buy and study the recently published first volume of
Lyell's "Principles." As an orthodox geologist of the then dominant
catastrophic school, Henslow accompanied his recommendation with the
admonition on no account to adopt Lyell's general views. But the warning
fell on deaf ears, and it is hardly too much to say that Darwin's greatest
work is the outcome of the unflinching application to Biology of the
leading idea and the method applied in the "Principles" to geology.
[Footnote: "After my return to England it appeared to me that by following
the example of Lyell in Geology, and by collecting all facts which bore in
any way on the variation of animals and plants under domestication and
nature, some light might perhaps be thrown on the whole subject [of the
origin of species]." (I. p. 83.) See also the dedication of the second
edition of the _Journal of a Naturalist_]. Finally, it was through
Henslow, and at his suggestion, that Darwin was offered the appointment to
the "Beagle" as naturalist.
During the latter part of Darwin's residence at Cambridge the prospect of
entering the Church, though the plan was never formally renounced, seems to
have grown very shadowy. Humboldt's "Personal Narrative," and Herschel's
"Introduction to the Study of Natural Philosophy," fell in his way and
revealed to him his real vocation. The impression made by the former work
was very strong. "My whole course of life," says Darwin in sending a
message to Humboldt, "is due to having read and re-read, as a youth, his
personal narrative." (I. p. 336.) The description of Teneriffe inspired
Darwin with such a strong desire to visit the island, that he took some
steps towards going there--inquiring about ships, and so on.
But, while this project was fermenting, Henslow, who had been asked to
recommend a naturalist for Captain Fitzroy's projected expedition, at once
thought of his pupil. In his letter of the 24th August, 1831, he says: "I
have stated that I consider you to be the best qualified person I know of
who is likely to undertake such a situation. I state this--not on the
supposition of your being a _finished_ naturalist, but as amply
qualified for collecting, observing, and noting anything worthy to be noted
in Natural History.... The voyage is to last two years, and if you take
plenty of books with you, anything you please may be done." (I. p. 193.)
The state of the case could not have been better put. Assuredly the young
naturalist's theoretical and practical scientific training had gone no
further than might suffice for the outfit of an intelligent collector and
note-taker. He was fully conscious of the fact, and his ambition hardly
rose above the hope that he should bring back materials for the scientific
"lions" at home of sufficient excellence to prevent them from turning and
rending him. (I. p. 248.)
But a fourth educational experiment was to be tried. This time Nature took
him in hand herself and showed him the way by which, to borrow Henslow's
prophetic phrase, "anything he pleased might be done."
The conditions of life presented by a ship-of-war of only 242 tons burthen,
would not, _primâ facie_, appear to be so favourable to intellectual
development as those offered by the cloistered retirement of Christ's
College. Darwin had not even a cabin to himself; while, in addition to the
hindrances and interruptions incidental to sea-life, which can be
appreciated only by those who have had experience of them, sea-sickness
came on whenever the little ship was "lively"; and, considering the
circumstances of the cruise, that must have been her normal state.
Nevertheless, Darwin found on board the "Beagle" that which neither the
pedagogues of Shrewsbury, nor the professoriate of Edinburgh, nor the
tutors of Cambridge had managed to give him. "I have always felt that I owe
to the voyage the first real training or education of my mind (I. p. 61);"
and in a letter written as he was leaving England, he calls the voyage on
which he was starting, with just insight, his "second life." (I. p. 214.)
Happily for Darwin's education, the school time of the "Beagle" lasted five
years instead of two; and the countries which the ship visited were
singularly well fitted to provide him with object-lessons, on the nature of
things, of the greatest value.
While at sea, he diligently collected, studied, and made copious notes upon
the surface Fauna. But with no previous training in dissection, hardly any
power of drawing, and next to no knowledge of comparative anatomy, his
occupation with work of this kind--notwithstanding all his zeal and
industry--resulted, for the most part, in a vast accumulation of useless
manuscript. Some acquaintance with the marine _Crustacea_,
observations on _Planariæ_ and on the ubiquitous _Sagitta_, seem
to have been the chief results of a great amount of labour in this
direction.
It was otherwise with the terrestrial phenomena which came under the
voyager's notice: and Geology very soon took her revenge for the scorn
which the much-bored Edinburgh student had poured upon her. Three weeks
after leaving England the ship touched land for the first time at St. Jago,
in the Cape de Verd Islands, and Darwin found his attention vividly engaged
by the volcanic phenomena and the signs of upheaval which the island
presented. His geological studies had already indicated the direction in
which a great deal might be done, beyond collecting; and it was while
sitting beneath a low lava cliff on the shore of this island, that a sense
of his real capability first dawned upon Darwin, and prompted the ambition
to write a book on the geology of the various countries visited. (I. p.
66.) Even at this early date, Darwin must have thought much on geological
topics, for he was already convinced of the superiority of Lyell's views to
those entertained by the catastrophists [Footnote: "I had brought with me
the first volume of Lyell's _Principles of Geology_, which I studied
attentively; and the book was of the highest service to me in many ways.
The very first place which I examined, namely, St. Jago, in the Cape de
Verd Islands, showed me clearly the wonderful superiority of Lyell's manner
of treating Geology, compared with that of any other author whose works I
had with me or ever afterwards read "-(I. p. 62.)]; and his subsequent
study of the tertiary deposits and of the terraced gravel beds of South
America was eminently fitted to strengthen that conviction. The letters
from South America contain little reference to any scientific topic except
geology; and even the theory of the formation of coral reefs was prompted
by the evidence of extensive and gradual changes of level afforded by the
geology of South America; "No other work of mine," he says, "was begun in
so deductive a spirit as this; for the whole theory was thought out on the
West Coast of South America, before I had seen a true coral reef. I had,
therefore, only to verify and extend my views by a careful examination of
living reefs." (I. p. 70.) In 1835, when starting from Lima for the
Galapagos, he recommends his friend, W. D. Fox, to take up geology:--"There
is so much larger a field for thought than in the other branches of Natural
History. I am become a zealous disciple of Mr. Lyell's views, as made known
in his admirable book. Geologising in South America, I am tempted to carry
parts to a greater extent even than he does. Geology is a capital science
to begin with, as it requires nothing but a little reading, thinking, and
hammering." (I. p. 263.) The truth of the last statement, when it was
written, is a curious mark of the subsequent progress of geology. Even so
late as 1836, Darwin speaks of being "much more inclined for geology than
the other branches of Natural History." (I. p. 275.)
At the end of the letter to Mr. Fox, however, a little doubt is expressed
whether zoological studies might not, after all, have been more profitable;
and an interesting passage in the "Autobiography" enables us to understand
the origin of this hesitation.
"During the voyage of the 'Beagle' I had been deeply impressed by
discovering in the Pampean formation great fossil animals covered with
armour like that on the existing armadillos; secondly, by the manner in
which closely-allied animals replace one another in proceeding southwards
over the continent; and, thirdly, by the South American character of most
of the productions of the Galapagos Archipelago, and, more especially, by
the manner in which they differ slightly on each island of the group; some
of the islands appearing to be very ancient in a geological sense.
"It was evident that such facts as these, as well as many others, could
only be explained on the supposition that species gradually become
modified; and the subject haunted me. But it was equally evident that
neither the action of the surrounding conditions, nor the will of the
organisms (especially in the case of plants) could account for the
innumerable cases in which organisms of every kind are beautifully adapted
to their habits of life; for instance, a woodpecker or a tree-frog to climb
trees, or a seed for dispersal by hooks or plumes. I had always been much
struck by such adaptations, and until these could be explained it seemed to
me almost useless to endeavour to prove by indirect evidence that species
have been modified." (I. p. 82.)
The facts to which reference is here made were, without doubt, eminently
fitted to attract the attention of a philosophical thinker; but, until the
relations of the existing with the extinct species and of the species of
the different geographical areas with one another, were determined with
some exactness, they afforded but an unsafe foundation for speculation. It
was not possible that this determination should have been effected before
the return of the "Beagle" to England; and thus the date which Darwin
(writing in 1837) assigns to the dawn of the new light which was rising in
his mind becomes intelligible. [Footnote: I am indebted to Mr. F. Darwin
for the knowledge of a letter addressed by his father to Dr. Otto Zacharias
in 1877 which contains the following paragraph, confirmatory of the view
expressed above: "When I was on board the _Beagle_, I believed in the
permanence of species, but, as far as I can remember, vague doubts
occasionally flitted across my mind. On my return home in the autumn of
1836, I immediately began to prepare my journal for publication, and then
saw how many facts indicated the common descent of species, so that in
July, 1837, I opened a note-book to record any facts which might bear on
the question. But I did not become convinced that species were mutable
until, I think, two or three years had elapsed."]
"In July opened first note-book on Transmutation of Species. Had been
greatly struck from about the month of previous March on character of South
American fossils and species on Galapagos Archipelago. These facts
(especially latter) origin of all my views." (I. p. 276.)
From March, 1837, then, Darwin, not without many misgivings and
fluctuations of opinion, inclined towards transmutation as a provisional
hypothesis. Three months afterwards he is hard at work collecting facts for
the purpose of testing the hypothesis; and an almost apologetic passage in
a letter to Lyell shows that, already, the attractions of biology are
beginning to predominate over those of geology.
"I have lately been sadly tempted to be idle--[Footnote: Darwin generally
uses the word "idle" in a peculiar sense. He means by it working hard at
something he likes when he ought to be occupied with a less attractive
subject. Though it sounds paradoxical, there is a good deal to be said in
favour of this view of pleasant work.]that is, as far as pure Geology is
concerned--by the delightful number of new views which have been coming in
thickly and steadily--on the classification and affinities and instincts of
animals--bearing on the question of species. Note-book after note-book has
been filled with facts which begin to group themselves _clearly_ under
sub-laws." (I. p. 298.)
The problem which was to be Darwin's chief subject of occupation for the
rest of his life thus presented itself, at first, mainly under its
distributional aspect. Why do species present certain relations in space
and in time? Why are the animals and plants of the Galapagos Archipelago so
like those of South America and yet different from them? Why are those of
the several islets more or less different from one another? Why are the
animals of the latest geological epoch in South America similar in
_facies_ to those which exist in the same region at the present day,
and yet specifically or generically different?
The reply to these questions, which was almost universally received fifty
years ago, was that animals and plants were created such as they are; and
that their present distribution, at any rate so far as terrestrial
organisms are concerned, has been effected by the migration of their
ancestors from the region in which the ark stranded after the subsidence of
the deluge. It is true that the geologists had drawn attention to a good
many tolerably serious difficulties in the way of the diluvial part of this
hypothesis, no less than to the supposition that the work of creation had
occupied only a brief space of time. But even those, such as Lyell, who
most strenuously argued in favour of the sufficiency of natural causes for
the production of the phenomena of the inorganic world, held stoutly by the
hypothesis of creation in the case of those of the world of life.
For persons who were unable to feel satisfied with the fashionable
doctrine, there remained only two alternatives--the hypothesis of
spontaneous generation, and that of descent with modification. The former
was simply the creative hypothesis with the creator left out; the latter
had already been propounded by De Maillet and Erasmus Darwin, among others;
and, later, systematically expounded by Lamarck. But in the eyes of the
naturalist of the "Beagle" (and, probably, in those of most sober
thinkers), the advocates of transmutation had done the doctrine they
expounded more harm than good.
Darwin's opinion of the scientific value of the "Zoonomia" has already been
mentioned. His verdict on Lamarck is given in the following passage of a
letter to Lyell (March, 1863):--
"Lastly, you refer repeatedly to my view as a modification of Lamarck's
doctrine of development and progression. If this is your deliberate opinion
there is nothing to be said, but it does not seem so to me. Plato, Buffon,
my grandfather, before Lamarck and others, propounded the _obvious_
view that if species were not created separately they must have descended
from other species, and I can see nothing else in common between the
"Origin" and Lamarck. I believe this way of putting the case is very
injurious to its acceptance, as it implies necessary progression, and
closely connects Wallace's and my views with what I consider, after two
deliberate readings, as a wretched book, and one from which (I well
remember to my surprise) I gained nothing."
"But," adds Darwin with a little touch of banter, "I know you rank it
higher, which is curious, as it did not in the least shake your belief."
(III. p. 14; see also p. 16, "to me it was an absolutely useless book.")
Unable to find any satisfactory theory of the process of descent with
modification in the works of his predecessors, Darwin proceeded to lay the
foundations of his own views independently; and he naturally turned, in the
first place, to the only certainly known examples of descent with
modification, namely, those which are presented by domestic animals and
cultivated plants. He devoted himself to the study of these cases with a
thoroughness to which none of his predecessors even remotely approximated;
and he very soon had his reward in the discovery "that selection was the
keystone of man's success in making useful races of animals and plants."
(I. p. 83.)
This was the first step in Darwin's progress, though its immediate result
was to bring him face to face with a great difficulty. "But how selection
could be applied to organisms living in a state of nature remained for some
time a mystery to me." (I. p. 83.)
The key to this mystery was furnished by the accidental perusal of the
famous essay of Malthus "On Population" in the autumn of 1838. The
necessary result of unrestricted multiplication is competition for the
means of existence. The success of one competitor involves the failure of
the rest, that is, their extinction; and this "selection" is dependent on
the better adaptation of the successful competitor to the conditions of the
competition. Variation occurs under natural, no less than under artificial,
conditions. Unrestricted multiplication implies the competition of
varieties and the selection of those which are relatively best adapted to
the conditions.
Neither Erasmus Darwin, nor Lamarck, had any inkling of the possibility of
this process of "natural selection"; and though it had been foreshadowed by
Wells in 1813, and more fully stated by Matthew in 1831, the speculations
of the latter writer remained unknown to naturalists until after the
publication of the "Origin of Species."
Darwin found in the doctrine of the selection of favourable variations by
natural causes, which thus presented itself to his mind, not merely a
probable theory of the origin of the diverse species of living forms, but
that explanation of the phenomena of adaptation, which previous
speculations had utterly failed to give. The process of natural selection
is, in fact, dependent on adaptation--it is all one, whether one says that
the competitor which survives is the "fittest" or the "best adapted." And
it was a perfectly fair deduction that even the most complicated
adaptations might result from the summation of a long series of simple
favourable variations.
Darwin notes as a serious defect in the first sketch of his theory that he
had omitted to consider one very important problem, the solution of which
did not occur to him till some time afterwards. "This problem is the
tendency in organic beings descended from the same stock to diverge in
character as they become modified.... The solution, as I believe, is that
the modified offspring of all dominant and increasing forms tend to become
adapted to many and highly diversified places in the economy of nature."
(I. p. 84.)
It is curious that so much importance should be attached to this
supplementary idea. It seems obvious that the theory of the origin of
species by natural selection necessarily involves the divergence of the
forms selected. An individual which varies, _ipso facto_ diverges from
the type of its species; and its progeny, in which the variation becomes
intensified by selection, must diverge still more, not only from the parent
stock, but from any other race of that stock starting from, a variation of
a different character. The selective process could not take place unless
the selected variety was either better adapted to the conditions than the
original stock, or adapted to other conditions than the original stock. In
the first case, the original stock would be sooner or later extirpated; in
the second, the type, as represented by the original stock and the variety,
would occupy more diversified stations than it did before.
The theory, essentially such as it was published fourteen years later, was
written out in 1844, and Darwin was so fully convinced of the importance of
his work, as it then stood, that he made special arrangements for its
publication in case of his death. But it is a singular example of reticent
fortitude, that, although for the next fourteen years the subject never
left his mind, and during the latter half of that period he was constantly
engaged in amassing facts bearing upon it from wide reading, a colossal
correspondence, and a long series of experiments, only two or three friends
were cognisant of his views. To the outside world he seemed to have his
hands quite sufficiently full of other matters. In 1844, he published his
observations on the volcanic islands visited during the voyage of the
"Beagle." In 1845, a largely remodelled edition of his "Journal" made its
appearance, and immediately won, as it has ever since held, the favour of
both the scientific and the unscientific public. In 1846, the "Geological
Observations in South America" came out, and this book was no sooner
finished than Darwin set to work upon the Cirripedes. He was led to
undertake this long and heavy task, partly by his desire to make out the
relations of a very anomalous form which he had discovered on the coast of
Chili; and partly by a sense of "presumption in accumulating facts and
speculating on the subject of variation without having worked out my due
share of species." (II. p. 31.) The eight or nine years of labour, which
resulted in a monograph of first-rate importance in systematic zoology (to
say nothing of such novel points as the discovery of complemental males),
left Darwin no room to reproach himself on this score, and few will share
his "doubt whether the work was worth the consumption of so much time." (I.
p. 82.)
In science no man can safely speculate about the nature and relation of
things with which he is unacquainted at first hand, and the acquirement of
an intimate and practical knowledge of the process of species-making and of
all the uncertainties which underlie the boundaries between species and
varieties, drawn by even the most careful and conscientious systematists
[Footnote: "After describing a set of forms as distinct species, tearing up
my MS., and making them one species, tearing that up and making them
separate, and then making them one again (which has happened to me), I have
gnashed my teeth, cursed species, and asked what sin I had committed to be
so punished." (II. p. 40.) Is there any naturalist provided with a logical
sense and a large suite of specimens, who has not undergone pangs of the
sort described in this vigorous paragraph, which might, with advantage, be
printed on the title-page of every systematic monograph as a warning to the
uninitiated?] were of no less importance to the author of the "Origin of
Species" than was the bearing of the Cirripede work upon "the principles of
a natural classification." (I. p. 81.) No one, as Darwin justly observes,
has a "right to examine the question of species who has not minutely
described many." (II. p. 39.)
In September, 1854, the Cirripede work was finished, "ten thousand
barnacles" had been sent "out of the house, all over the world," and Darwin
had the satisfaction of being free to turn again to his "old notes on
species." In 1855, he began to breed pigeons, and to make observations on
the effects of use and disuse, experiments on seeds, and so on, while
resuming his industrious collection of facts, with a view "to see how far
they favour or are opposed to the notion that wild species are mutable or
immutable. I mean with my utmost power to give all arguments and facts on
both sides. I have a _number_ of people helping me every way, and
giving me most valuable assistance; but I often doubt whether the subject
will not quite overpower me." (II. p. 49.)
Early in 1856, on Lyell's advice, Darwin began to write out his views on
the origin of species on a scale three or four times as extensive as that
of the work published in 1859. In July of the same year he gave a brief
sketch of his theory in a letter to Asa Gray; and, in the year 1857, his
letters to his correspondents show him to be busily engaged on what he
calls his "big book." (II. pp. 85, 94.) In May, 1857, Darwin writes to
Wallace: "I am now preparing my work [on the question how and in what way
do species and varieties differ from each other] for publication, but I
find the subject so very large, that, though I have written many chapters,
I do not suppose I shall go to press for two years." (II. p. 95.) In
December, 1857, he writes, in the course of a long letter to the same
correspondent, "I am extremely glad to hear that you are attending to
distribution in accordance with theoretical ideas. I am a firm believer
that without speculation there is no good and original observation." (II.
p. 108.) [Footnote: The last remark contains a pregnant truth, but it must
be confessed it hardly squares with the declaration in the
_Autobiography_, (I. p. 83), that he worked on "true Baconian
principles."] In June, 1858, he received from Mr. Wallace, then in the
Malay Archipelago, an "Essay on the tendency of varieties to depart
indefinitely from the original type," of which Darwin says, "If Wallace had
my MS. sketch written out in 1842 he could not have made a better short
abstract! Even his terms stand now as heads of my chapters. Please return
me the MS., which he does not say he wishes me to publish, but I shall, of
course, at once write and offer to send it to any journal. So all my
originality, whatever it may amount to, will be smashed, though my book, if
ever it will have any value, will not be deteriorated; as all the labour
consists in the application of the theory." (II. p. 116.)
Thus, Darwin's first impulse was to publish Wallace's essay without note or
comment of his own. But, on consultation with Lyell and Hooker, the latter
of whom had read the sketch of 1844, they suggested, as an undoubtedly more
equitable course, that extracts from the MS. of 1844 and from the letter to
Dr. Asa Gray should be communicated to the Linnean Society along with
Wallace's essay. The joint communication was read on July 1, 1858, and
published under the title "On the Tendency of Species to form Varieties;
and on the Perpetuation of Varieties and Species by Natural Means of
Selection." This was followed, on Darwin's part, by the composition of a
summary account of the conclusions to which his twenty years' work on the
species question had led him. It occupied him for thirteen months, and
appeared in November, 1859, under the title "On the Origin of Species by
means of Natural Selection or the Preservation of Favoured Races in the
Struggle of Life."
It is doubtful if any single book, except the "Principia," ever worked so
great and so rapid a revolution in science, or made so deep an impression
on the general mind. It aroused a tempest of opposition and met with
equally vehement support, and it must be added that no book has been more
widely and persistently misunderstood by both friends and foes. In 1861,
Darwin remarks to a correspondent, "You understand my book perfectly, and
that I find a very rare event with my critics." (I. p. 313.) The immense
popularity which the "Origin" at once acquired was no doubt largely due to
its many points of contact with philosophical and theological questions in
which every intelligent man feels a profound interest; but a good deal must
be assigned to a somewhat delusive simplicity of style, which tends to
disguise the complexity and difficulty of the subject, and much to the
wealth of information on all sorts of curious problems of natural history,
which is made accessible to the most unlearned reader. But long occupation
with the work has led the present writer to believe that the "Origin of
Species" is one of the hardest of books to master; [Footnote: He is
comforted to find that probably the best qualified judge among all the
readers of the _Origin_ in 1859 was of the same opinion. Sir J. Hooker
writes, "It is the very hardest book to read, to full profit, that I ever
tried." (II. p. 242.)] and he is justified in this conviction by observing
that although the "Origin" has been close on thirty years before the world,
the strangest misconceptions of the essential nature of the theory therein
advocated are still put forth by serious writers.
Although, then, the present occasion is not suitable for any detailed
criticism of the theory, or of the objections which have been brought
against it, it may not be out of place to endeavour to separate the
substance of the theory from its accidents; and to show that a variety not
only of hostile comments, but of friendly would-be improvements lose their
_raison d'être_ to the careful student. Observation proves the
existence among all living beings of phenomena of three kinds, denoted by
the terms heredity, variation, and multiplication. Progeny tend to resemble
their parents; nevertheless all their organs and functions are susceptible
of departing more or less from the average parental character; and their
number is in excess of that of their parents. Severe competition for the
means of living, or the struggle for existence, is a necessary consequence
of unlimited multiplication; while selection, or the preservation of
favourable variations and the extinction of others, is a necessary
consequence of severe competition. "Favourable variations" are those which
are better adapted to surrounding conditions. It follows, therefore, that
every variety which is selected into a species is so favoured and preserved
in consequence of being, in some one or more respects, better adapted to
its surroundings than its rivals. In other words, every species which
exists, exists in virtue of adaptation, and whatever accounts for that
adaptation accounts for the existence of the species.
To say that Darwin has put forward a theory of the adaptation of species,
but not of their origin, is therefore to misunderstand the first principles
of the theory. For, as has been pointed out, it is a necessary consequence
of the theory of selection that every species must have some one or more
structural or functional peculiarities, in virtue of the advantage
conferred by which, it has fought through the crowd of its competitors and
achieved a certain duration. In this sense, it is true that every species
has been "originated" by selection.
There is another sense, however, in which it is equally true that selection
originates nothing. "Unless profitable variations ... occur natural
selection can do nothing" ("Origin," Ed. I. p. 82). "Nothing can be
effected unless favourable variations occur" (_ibid_., p. 108). "What
applies to one animal will apply throughout time to all animals--that is,
if they vary--for otherwise natural selection can do nothing. So it will be
with plants" (_ibid_., p. 113). Strictly speaking, therefore, the
origin of species in general lies in variation; while the origin of any
particular species lies, firstly, in the occurrence, and secondly, in the
selection and preservation of a particular variation. Clearness on this
head will relieve one from the necessity of attending to the fallacious
assertion that natural selection is a _deus ex machinâ_, or occult
agency.
Those, again, who confuse the operation of the natural causes which bring
about variation and selection with what they are pleased to call "chance"
can hardly have read the opening paragraph of the fifth chapter of the
"Origin" (Ed. I, p. 131): "I have sometimes spoken as if the variations ...
had been due to chance. This is of course a wholly incorrect expression,
but it seems to acknowledge plainly our ignorance of the cause of each
particular variation."
Another point of great importance to the right comprehension of the theory,
is, that while every species must needs have some adaptive advantageous
characters to which it owes its preservation by selection, it may possess
any number of others which are neither advantageous nor disadvantageous,
but indifferent, or even slightly disadvantageous. (_Ibid_., p. 81.)
For variations take place, not merely in one organ or function at a time,
but in many; and thus an advantageous variation, which gives rise to the
selection of a new race or species, may be accompanied by others which are
indifferent, but which are just as strongly hereditary as the advantageous
variations. The advantageous structure is but one product of a modified
general constitution which may manifest itself by several other products;
and the selective process carries the general constitution along with the
advantageous special peculiarity. A given species of plant may owe its
existence to the selective adaptation of its flowers to insect fertilisers;
but the character of its leaves may be the result of variations of an
indifferent character. It is the origin of variations of this kind to which
Darwin refers in his frequent reference to what he calls "laws of
correlation of growth" or "correlated variation."
These considerations lead us further to see the inappropriateness of the
objections raised to Darwin's theory on the ground that natural selection
does not account for the first commencements of useful organs. But it does
not pretend to do so. The source of such commencements is necessarily to be
sought in different variations, which remain unaffected by selection until
they have taken such a form as to become utilisable in the struggle for
existence.
It is not essential to Darwin's theory that anything more should be assumed
than the facts of heredity, variation, and unlimited multiplication; and
the validity of the deductive reasoning as to the effect of the last (that
is, of the struggle for existence which it involves) upon the varieties
resulting from the operation of the former. Nor is it essential that one
should take up any particular position in regard to the mode of variation,
whether, for example, it takes place _per saltum_ or gradually;
whether it is definite in character or indefinite. Still less are those who
accept the theory bound to any particular views as to the causes of
heredity or of variation.
That Darwin held strong opinions on some or all of these points may be
quite true; but, so far as the theory is concerned, they must be regarded
as _obiter dicta_. With respect to the causes of variation, Darwin's
opinions are, from first to last, put forward altogether tentatively. In
the first edition of the "Origin," he attributes the strongest influence to
changes in the conditions of life of parental organisms, which he appears
to think act on the germ through the intermediation of the sexual organs.
He points out, over and over again, that habit, use, disuse, and the direct
influence of conditions have some effect, but he does not think it great,
and he draws attention to the difficulty of distinguishing between effects
of these agencies and those of selection. There is, however, one class of
variations which he withdraws from the direct influence of selection,
namely, the variations in the fertility of the sexual union of more or less
closely allied forms. He regards less fertility, or more or less complete
sterility, as "incidental to other acquired differences." (_Ibid_., p.
245.)
Considering the difficulties which surround the question of the causes of
variation, it is not to be wondered at, that Darwin should have inclined,
sometimes, rather more to one and, sometimes, rather more to another of the
possible alternatives. There is little difference between the last edition
of the "Origin" (1872) and the first on this head. In 1876, however, he
writes to Moritz Wagner, "In my opinion, the greatest error which I have
committed has been not allowing sufficient weight to the direct action of
the environments, i.e., food, climate, &c., independently of natural
selection. ...When I wrote the 'Origin,' and for some years afterwards, I
could find little good evidence of the direct action of the environment;
now there is a large body of evidence, and your case of the Saturnia is one
of the most remarkable of which I have heard." (III, p. 159.) But there is
really nothing to prevent the most tenacious adherent to the theory of
natural selection from taking any view he pleases as to the importance of
the direct influence of conditions and the hereditary transmissibility of
the modifications which they produce. In fact, there is a good deal to be
said for the view that the so-called direct influence of conditions is
itself a case of selection. Whether the hypothesis of Pangenesis be
accepted or rejected, it can hardly be doubted that the struggle for
existence goes on not merely between distinct organisms, but between the
physiological units of which each organism is composed, and that changes in
external conditions favour some and hinder others.
After a short stay in Cambridge, Darwin resided in London for the first
five years which followed his return to England; and for three years, he
held the post of Secretary to the Geological Society, though he shared to
the full his friend Lyell's objection to entanglement in such engagements.
In fact, he used to say in later life, more than half in earnest, that he
gave up hoping for work from men who accepted official duties and,
especially, Government appointments. Happily for him, he was exempted from
the necessity of making any sacrifice of this kind, but an even heavier
burden was laid upon him. During the earlier half of his voyage Darwin
retained the vigorous health of his boyhood, and indeed proved himself to
be exceptionally capable of enduring fatigue and privation. An anomalous
but severe disorder, which laid him up for several weeks at Valparaiso in
1834, however, seems to have left its mark on his constitution; and, in the
later years of his London life, attacks of illness, usually accompanied by
severe vomiting and great prostration of strength, became frequent. As he
grew older, a considerable part of every day, even at his best times, was
spent in misery; while, not unfrequently, months of suffering rendered work
of any kind impossible. Even Darwin's remarkable tenacity of purpose and
methodical utilisation of every particle of available energy could not have
enabled him to achieve a fraction of the vast amount of labour he got
through, in the course of the following forty years, had not the wisest and
the most loving care unceasingly surrounded him from the time of his
marriage in 1839. As early as 1842, the failure of health was so marked
that removal from London became imperatively necessary; and Darwin
purchased a house and grounds at Down, a solitary hamlet in Kent, which was
his home for the rest of his life. Under the strictly regulated conditions
of a valetudinarian existence, the intellectual activity of the invalid
might have put to shame most healthy men; and, so long as he could hold his
head up, there was no limit to the genial kindness of thought and action
for all about him. Those friends who were privileged to share the intimate
life of the household at Down have an abiding memory of the cheerful
restfulness which pervaded and characterised it.
After mentioning his settlement at Down, Darwin writes in his
Autobiography:--
"My chief enjoyment and sole employment throughout life has been scientific
work; and the excitement from such work makes me, for the time, forget, or
drives quite away, my daily discomfort. I have, therefore, nothing to
record during the rest of my life, except the publication of my several
books." (I, p. 79.)
Of such works published subsequently to 1859, several are monographic
discussions of topics briefly dealt with in the "Origin," which, it must
always be recollected, was considered by the author to be merely an
abstract of an _opus majus_.
The earliest of the books which may be placed in this category, "On the
Various Contrivances by which Orchids are Fertilised by Insects," was
published in 1862, and whether we regard its theoretical significance, the
excellence of the observations and the ingenuity of the reasonings which it
records, or the prodigious mass of subsequent investigation of which it has
been the parent, it has no superior in point of importance. The conviction
that no theory of the origin of species could be satisfactory which failed
to offer an explanation of the way in which mechanisms involving
adaptations of structure and function to the performance of certain
operations are brought about, was, from the first, dominant in Darwin's
mind. As has been seen, he rejected Lamarck's views because of their
obvious incapacity to furnish such an explanation in the case of the great
majority of animal mechanisms, and in that of all those presented by the
vegetable world.
So far back as 1793, the wonderful work of Sprengel had established, beyond
any reasonable doubt, the fact that, in a large number of cases, a flower
is a piece of mechanism the object of which is to convert insect visitors
into agents of fertilisation. Sprengel's observations had been most
undeservedly neglected and well-nigh forgotten; but Robert Brown having
directed Darwin's attention to them in 1841, he was attracted towards the
subject, and verified many of Sprengel's statements. (III, p. 258.) It may
be doubted whether there was a living botanical specialist, except perhaps
Brown, who had done as much. If, however, adaptations of this kind were to
be explained by natural selection, it was necessary to show that the plants
which were provided with mechanisms for ensuring the aid of insects as
fertilisers, were by so much the better fitted to compete with their
rivals. This Sprengel had not done. Darwin had been attending to cross
fertilisation in plants so far back as 1839, from having arrived, in the
course of his speculations on the origin of species, at the conviction
"that crossing played an important part in keeping specific forms constant"
(I, p. 90). The further development of his views on the importance of cross
fertilisation appears to have taken place between this time and 1857, when
he published his first papers on the fertilisation of flowers in the
"Gardener's Chronicle." If the conclusion at which he ultimately arrived,
that cross fertilisation is favourable to the fertility of the parent and
to the vigour of the offspring, is correct, then it follows that all those
mechanisms which hinder self-fertilisation and favour crossing must be
advantageous in the struggle for existence; and, the more perfect the
action of the mechanism, the greater the advantage. Thus the way lay open
for the operation of natural selection in gradually perfecting the flower
as a fertilisation-trap. Analogous reasoning applies to the fertilising
insect. The better its structure is adapted to that of the trap, the more
will it be able to profit by the bait, whether of honey or of pollen, to
the exclusion of its competitors. Thus, by a sort of action and reaction, a
two-fold series of adaptive modifications will be brought about.
In 1865, the important bearing of this subject on his theory led Darwin to
commence a great series of laborious and difficult experiments on the
fertilisation of plants, which occupied him for eleven years, and furnished
him with the unexpectedly strong evidence in favour of the influence of
crossing which he published in 1876, under the title of "The Effects of
Cross and Self Fertilisation in the Vegetable Kingdom." Incidentally, as it
were, to this heavy piece of work, he made the remarkable series of
observations on the different arrangements by which crossing is favoured
and, in many cases, necessitated, which appeared in the work on "The
Different Forms of Flowers in Plants of the same Species" in 1877.
In the course of the twenty years during which Darwin was thus occupied in
opening up new regions of investigation to the botanist and showing the
profound physiological significance of the apparently meaningless
diversities of floral structure, his attention was keenly alive to any
other interesting phenomena of plant life which came in his way. In his
correspondence, he not unfrequently laughs at himself for his ignorance of
systematic botany; and his acquaintance with vegetable anatomy and
physiology was of the slenderest. Nevertheless, if any of the less common
features of plant life came under his notice, that imperious necessity of
seeking for causes which nature had laid upon him, impelled, and indeed
compelled, him to inquire the how and the why of the fact, and its bearing
on his general views. And as, happily, the atavic tendency to frame
hypotheses was accompanied by an equally strong need to test them by
well-devised experiments, and to acquire all possible information before
publishing his results, the effect was that he touched no topic without
elucidating it.
Thus the investigation of the operations of insectivorous plants, embodied
in the work on that topic published in 1875, was started fifteen years
before, by a passing observation made during one of Darwin's rare holidays.
"In the summer of 1860, I was idling and resting near Hartfield, where two
species of Drosera abound; and I noticed that numerous insects had been
entrapped by the leaves. I carried home some plants, and on giving them
some insects saw the movements of the tentacles, and this made me think it
possible that the insects were caught for some special purpose.
Fortunately, a crucial test occurred to me, that of placing a large number
of leaves in various nitrogenous and non-nitrogenous fluids of equal
density; and as soon as I found that the former alone excited energetic
movements, it was obvious that here was a fine new field for
investigation." (I, p. 95.)
The researches thus initiated led to the proof that plants are capable of
secreting a digestive fluid like that of animals, and of profiting by the
result of digestion; whereby the peculiar apparatuses of the insectivorous
plants were brought within the scope of natural selection. Moreover, these
inquiries widely enlarged our knowledge of the manner in which stimuli are
transmitted in plants, and opened up a prospect of drawing closer the
analogies between the motor processes of plants and those of animals.
So with respect to the books on "Climbing Plants" (1875), and on the "Power
of Movement in Plants" (1880), Darwin says;--
"I was led to take up this subject by reading a short paper by Asa Gray,
published in 1858. He sent me some seeds, and on raising some plants I was
so much fascinated and perplexed by the revolving movements of the tendrils
and stems, which movements are really very simple, though appearing at
first sight very complex, that I procured various other kinds of climbing
plants and studied the whole subject.... Some of the adaptations displayed
by climbing plants are as beautiful as those of orchids for ensuring
cross-fertilisation." (I, p. 93.)
In the midst of all this amount of work, remarkable alike for its variety
and its importance, among plants, the animal kingdom was by no means
neglected. A large moiety of "The Variation of Animals and Plants under
Domestication" (1868), which contains the _pièces justificatives_ of
the first chapter of the "Origin," is devoted to domestic animals, and the
hypothesis of "pangenesis" propounded in the second volume applies to the
whole living world. In the "Origin" Darwin throws out some suggestions as
to the causes of variation, but he takes heredity, as it is manifested by
individual organisms, for granted, as an ultimate fact; pangenesis is an
attempt to account for the phenomena of heredity in the organism, on the
assumption that the physiological units of which the organism is composed
give off gemmules, which, in virtue of heredity, tend to reproduce the unit
from which they are derived.
That Darwin had the application of his theory to the origin of the human
species clearly in his mind in 1859, is obvious from a passage in the first
edition of "The Origin of Species." (Ed. I, p. 488.) "In the distant future
I see open fields for far more important researches. Psychology will be
based on a new foundation, that of the necessary acquirement of each mental
power and capacity by gradation. Light will be thrown on the origin of man
and his history." It is one of the curiosities of scientific literature,
that, in the face of this plain declaration, its author should have been
charged with concealing his opinions on the subject of the origin of man.
But he reserved the full statement of his views until 1871, when the
"Descent of Man" was published. The "Expression of the Emotions"
(originally intended to form only a chapter in the "Descent of Man") grew
into a separate volume, which appeared in 1872. Although always taking a
keen interest in geology, Darwin naturally found no time disposable for
geological work, even had his health permitted it, after he became
seriously engaged with the great problem of species. But the last of his
labours is, in some sense, a return to his earliest, inasmuch as it is an
expansion of a short paper read before the Geological Society more than
forty years before, and, as he says, "revived old geological thoughts" (I,
p. 98). In fact, "The Formation of Vegetable Mould through the Action of
Worms," affords as striking an example of the great results produced by the
long-continued operation of small causes as even the author of the
"Principles of Geology" could have desired.
In the early months of 1882 Darwin's health underwent a change for the
worse; attacks of giddiness and fainting supervened, and on the 19th of
April he died. On the 24th, his remains were interred in Westminster Abbey,
in accordance with the general feeling that such a man as he should not go
to the grave without some public recognition of the greatness of his work.
Mr. Darwin became a Fellow of the Royal Society in 1839; one of the Royal
Medals was awarded to him in 1853, and he received the Copley Medal in
1864. The "Life and Letters," edited with admirable skill and judgment by
Mr. Francis Darwin, gives a full and singularly vivid presentment of his
father's personal character, of his mode of work, and of the events of his
life. In the present brief obituary notice, the writer has attempted
nothing more than to select and put together those facts which enable us to
trace the intellectual evolution of one of the greatest of the many great
men of science whose names adorn the long roll of the Fellows of the Royal
Society.
XI
ON OUR KNOWLEDGE OF THE CAUSES OF THE PHENOMENA OF ORGANIC NATURE
[_Six Lectures to Working Men_.--1863.]
I. THE PRESENT CONDITION OF ORGANIC NATURE
When it was my duty to consider what subject I would select for the six
lectures which I shall now have the pleasure of delivering to you, it
occurred to me that I could not do better than endeavour to put before you
in a true light, or in what I might perhaps with more modesty call, that
which I conceive myself to be the true light, the position of a book which
has been more praised and more abused, perhaps, than any book which has
appeared for some years;--I mean Mr. Darwin's work on the "Origin of
Species." That work, I doubt not, many of you have read; for I know the
inquiring spirit which is rife among you. At any rate, all of you will have
heard of it,--some by one kind of report and some by another kind of
report; the attention of all and the curiosity of all have been probably
more or less excited on the subject of that work. All I can do, and all I
shall attempt to do, is to put before you that kind of judgment which has
been formed by a man, who, of course, is liable to judge erroneously; but,
at any rate, of one whose business and profession it is to form judgments
upon questions of this nature.
And here, as it will always happen when dealing with an extensive subject,
the greater part of my course--if, indeed, so small a number of lectures
can be properly called a course--must be devoted to preliminary matters, or
rather to a statement of those facts and of those principles which the work
itself dwells upon, and brings more or less directly before us. I have no
right to suppose that all or any of you are naturalists; and, even if you
were, the misconceptions and misunderstandings prevalent even among
naturalists, on these matters, would make it desirable that I should take
the course I now propose to take,--that I should start from the
beginning,--that I should endeavour to point out what is the existing state
of the organic world--that I should point out its past condition,--that I
should state what is the precise nature of the undertaking which Mr. Darwin
has taken in hand; that I should endeavour to show you what are the only
methods by which that undertaking can be brought to an issue, and to point
out to you how far the author of the work in question has satisfied those
conditions, how far he has not satisfied them, how far they are satisfiable
by man, and how far they are not satisfiable by man.
To-night, in taking up the first part of the question, I shall endeavour to
put before you a sort of broad notion of our knowledge of the condition of
the living world. There are many ways of doing this. I might deal with it
pictorially and graphically. Following the example of Humboldt in his
"Aspects of Nature," I might endeavour to point out the infinite variety of
organic life in every mode of its existence, with reference to the
variations of climate and the like; and such an attempt would be fraught
with interest to us all; but considering the subject before us, such a
course would not be that best calculated to assist us. In an argument of
this kind we must go further and dig deeper into the matter; we must
endeavour to look into the foundations of living Nature, if I may so say,
and discover the principles involved in some of her most secret operations.
I propose, therefore, in the first place, to take some ordinary animal with
which you are all familiar, and by easily comprehensible and obvious
examples drawn from it, to show what are the kind of problems which living
beings in general lay before us; and I shall then show you that the same
problems are laid open to us by all kinds of living beings. But, first, let
me say in what sense I have used the words "organic nature." In speaking of
the causes which lead to our present knowledge of organic nature, I have
used it almost as an equivalent of the word "living," and for this
reason,--that in almost all living beings you can distinguish several
distinct portions set apart to do particular things and work in a
particular way. These are termed "organs," and the whole together is called
"organic." And as it is universally characteristic of them, the term
"organic" has been very conveniently employed to denote the whole of living
nature,--the whole of the plant world, and the whole of the animal world.
Few animals can be more familiar to you than that whose skeleton is shown
on our diagram. You need not bother yourselves with this "_Equus
caballus_" written under it; that is only the Latin name of it, and does
not make it any better. It simply means the common horse. Suppose we wish
to understand all about the horse. Our first object must be to study the
structure of the animal. The whole of his body is inclosed within a hide, a
skin covered with hair; and if that hide or skin be taken off, we find a
great mass of flesh, or what is technically called muscle, being the
substance which by its power of contraction enables the animal to move.
These muscles move the hard parts one upon the other, and so give that
strength and power of motion which renders the horse so useful to us in the
performance of those services in which we employ him.
And then, on separating and removing the whole of this skin and flesh, you
have a great series of bones, hard structures, bound together with
ligaments, and forming the skeleton which is represented here.
In that skeleton there are a number of parts to be recognised. The long
series of bones, beginning from the skull and ending in the tail, is called
the spine, and those in front are the ribs; and then there are two pairs of
limbs, one before and one behind; and there are what we all know as the
fore-legs and the hind-legs. If we pursue our researches into the interior
of this animal, we find within the framework of the skeleton a great
cavity, or rather, I should say, two great cavities,--one cavity beginning
in the skull and running through the neck-bones, along the spine, and
ending in the tail, containing the brain and the spinal marrow, which are
extremely important organs. The second great cavity, commencing with the
mouth, contains the gullet, the stomach, the long intestine, and all the
rest of those internal apparatus which are essential for digestion; and
then in the same great cavity, there are lodged the heart and all the great
vessels going from it; and, besides that, the organs of respiration--the
lungs: and then the kidneys, and the organs of reproduction, and so on. Let
us now endeavour to reduce this notion of a horse that we now have, to some
such kind of simple expressions as can be at once, and without difficulty,
retained in the mind, apart from all minor details. If I make a transverse
section, that is, if I were to saw a dead horse across, I should find that,
if I left out the details, and supposing I took my section through the
anterior region, and through the fore-limbs, I should have here this kind
of section of the body (Fig. 1).
[Illustration: Fig. 1]
Here would be the upper part of the animal--that great mass of bones that
we spoke of as the spine (_a_, Fig. 1). Here I should have the
alimentary canal (_b_, Fig. 1). Here I should have the heart
(_c_, Fig. 1); and then you see, there would be a kind of double tube,
the whole being inclosed within the hide; the spinal marrow would be placed
in the upper tube (_a_, Fig. 1), and in the lower tube (_d d_,
Fig. 1), there would be the alimentary canal (_b_), and the heart
(_e_); and here I shall have the legs proceeding from each side. For
simplicity's sake, I represent them merely as stumps (_e e_, Fig. 1).
Now that is a horse--as mathematicians would say--reduced to its most
simple expression. Carry that in your minds, if you please, as a simplified
idea of the structure of the horse. The considerations which I have now put
before you belong to what we technically call the "Anatomy" of the horse.
Now, suppose we go to work upon these several parts,--flesh and hair, and
skin and bone, and lay open these various organs with our scalpels, and
examine them by means of our magnifying-glasses, and see what we can make
of them. We shall find that the flesh is made up of bundles of strong
fibres The brain and nerves, too, we shall find are made up of fibres, and
these queer-looking things that are called ganglionic corpuscles. If we
take a slice of the bone and examine it, we shall find that it is very like
this diagram of a section of the bone of on ostrich, though differing, of
course, in some details; and if we take any part whatsoever of the tissue,
and examine it, we shall find it all has a minute structure, visible only
under the microscope. All these parts constitute microscopic anatomy or
"Histology." These parts are constantly being changed; every part is
constantly growing, decaying, and being replaced during the life of the
animal. The tissue is constantly replaced by new material; and if you go
back to the young state of the tissue in the case of muscle, or in the case
of skin, or any of the organs I have mentioned, you will find that they all
come under the same condition. Every one of these microscopic filaments and
fibres (I now speak merely of the general character of the whole
process)--every one of these parts--could be traced down to some
modification of a tissue which can be readily divided into little particles
of fleshy matter, of that substance which is composed of the chemical
elements, carbon, hydrogen, oxygen, and nitrogen, having such a shape as
this (Fig. 2). These particles, into which all primitive tissues break up,
are called cells. If I were to make a section of a piece of the skin of my
hand, I should find that it was made up of these cells. If I examine the
fibres which form the various organs of all living animals, I should find
that all of them, at one time or other, had been formed out of a substance
consisting of similar elements; so that you see, just as we reduced the
whole body in the gross to that sort of simple expression given in Fig. 1,
so we may reduce the whole of the microscopic structural elements to a form
of even greater simplicity; just as the plan of the whole body may be so
represented in a sense (Fig. 1), so the primary structure of every tissue
may be represented by a mass of cells (Fig. 2).
[Illustration: Fig. 2.]
Having thus, in this sort of general way, sketched to you what I may call,
perhaps, the architecture of the body of the horse (what we term
technically its Morphology), I must now turn to another aspect. A horse is
not a mere dead structure: it is an active, living, working machine.
Hitherto we have, as it were, been looking at a steam-engine with the fires
out, and nothing in the boiler; but the body of the living animal is a
beautifully-formed active machine, and every part has its different work to
do in the working of that machine, which is what we call its life. The
horse, if you see him after his day's work is done, is cropping the grass
in the fields, as it may be, or munching the oats in his stable. What is he
doing? His jaws are working as a mill--and a very complex mill
too--grinding the corn, or crushing the grass to a pulp. As soon as that
operation has taken place, the food is passed down to the stomach, and
there it is mixed with the chemical fluid called the gastric juice, a
substance which has the peculiar property of making soluble and dissolving
out the nutritious matter in the grass, and leaving behind those parts
which are not nutritious; so that you have, first, the mill, then a sort of
chemical digester; and then the food, thus partially dissolved, is carried
back by the muscular contractions of the intestines into the hinder parts
of the body, while the soluble portions are taken up into the blood. The
blood is contained in a vast system of pipes, spreading through the whole
body, connected with a force-pump,--the heart,--which, by its position and
by the contractions of its valves, keeps the blood constantly circulating
in one direction, never allowing it to rest; and then, by means of this
circulation of the blood, laden as it is with the products of digestion,
the skin, the flesh, the hair, and every other part of the body, draws from
it that which it wants, and every one of these organs derives those
materials which are necessary to enable it to do its work.
The action of each of these organs, the performance of each of these
various duties, involve in their operation a continual absorption of the
matters necessary for their support, from the blood and a constant
formation of waste products, which are returned to the blood, and conveyed
by it to the lungs and the kidneys, which are organs that have allotted to
them the office of extracting, separating, and getting rid of these waste
products; and thus the general nourishment, labour, and repair of the whole
machine are kept up with order and regularity. But not only is it a machine
which feeds and appropriates to its own support the nourishment necessary
to its existence--it is an engine for locomotive purposes. The horse
desires to go from one place to another; and to enable it to do this, it
has those strong contractile bundles of muscles attached to the bones of
its limbs, which are put in motion by means of a sort of telegraphic
apparatus formed by the brain and the great spinal cord running through the
spine or backbone; and to this spinal cord are attached a number of fibres
termed nerves, which proceed to all parts of the structure. By means of
these the eyes, nose, tongue, and skin--all the organs of
perception--transmit impressions or sensations to the brain, which acts as
a sort of great central telegraph-office, receiving impressions and sending
messages to all parts of the body, and putting in motion the muscles
necessary to accomplish any movement that maybe desired. So that you have
here an extremely complex and beautifully-proportioned machine, with all
its parts working harmoniously together towards one common object--the
preservation of the life of the animal.
Now, note this: the horse makes up its waste by feeding, and its food is
grass or oats, or perhaps other vegetable products; therefore, in the long
run, the source of all this complex machinery lies in the vegetable
kingdom. But where does the grass, or the oat, or any other plant obtain
this nourishing food-producing material? At first it is a little seed,
which soon begins to draw into itself from the earth and the surrounding
air matters which in themselves contain no vital properties whatever; it
absorbs into its own substance water, an inorganic body; it draws into its
substance carbonic acid, an inorganic matter; and ammonia, another
inorganic matter, found in the air; and then, by some wonderful chemical
process, the details of which chemists do not yet understand, though they
are near foreshadowing them, it combines them into one substance, which is
known to us as "Protein," a complex compound of carbon, hydrogen, oxygen,
and nitrogen, which alone possesses the property of manifesting vitality
and of permanently supporting animal life. So that, you see, the waste
products of the animal economy, the effete materials which are continually
being thrown off by all living beings, in the form of organic matters, are
constantly replaced by supplies of the necessary repairing and rebuilding
materials drawn from the plants, which in their turn manufacture them, so
to speak, by a mysterious combination of those same inorganic materials.
Let us trace out the history of the horse in another direction. After a
certain time, as the result of sickness or disease, the effect of accident,
or the consequence of old age, sooner or later, the animal dies. The
multitudinous operations of this beautiful mechanism flag in their
performance, the horse loses its vigour, and after passing through the
curious series of changes comprised in its formation and preservation, it
finally decays, and ends its life by going back into that inorganic world
from which all but an inappreciable fraction of its substance was derived.
Its bones become mere carbonate and phosphate of lime; the matter of its
flesh, and of its other parts, becomes, in the long run, converted into
carbonic acid, into water, and into ammonia. You will now, perhaps,
understand the curious relation of the animal with the plant, of the
organic with the inorganic world, which is shown in this diagram.
[Illustration: Inorganic World Fig. 3.]
The plant gathers these inorganic materials together and makes them up into
its own substance. The animal eats the plant and appropriates the
nutritious portions to its own sustenance, rejects and gets rid of the
useless matters; and, finally, the animal itself dies, and its whole body
is decomposed and returned into the inorganic world. There is thus a
constant circulation from one to the other, a continual formation of
organic life from inorganic matters, and as constant a return of the matter
of living bodies to the inorganic world; so that the materials of which our
bodies are composed are largely, in all probability, the substances which
constituted the matter of long extinct creations, but which have in the
interval constituted a part of the inorganic world.
Thus we come to the conclusion, strange at first sight, that the MATTER
constituting the living world is identical with that which forms the
inorganic world. And not less true is it that, remarkable as are the powers
or, in other words, as are the FORCES which are exerted by living beings,
yet all these forces are either identical with those which exist in the
inorganic world, or they are convertible into them; I mean in just the same
sense as the researches of physical philosophers have shown that heat is
convertible into electricity, that electricity is convertible into
magnetism, magnetism into mechanical force or chemical force, and any one
of them with the other, each being measurable in terms of the other,--even
so, I say, that great law is applicable to the living world. Consider why
is the skeleton of this horse capable of supporting the masses of flesh and
the various organs forming the living body, unless it is because of the
action of the same forces of cohesion which combines together the particles
of matter composing this piece of chalk? What is there in the muscular
contractile power of the animal but the force which is expressible, and
which is in a certain sense convertible, into the force of gravity which it
overcomes? Or, if you go to more hidden processes, in what does the process
of digestion differ from those processes which are carried on in the
laboratory of the chemist? Even if we take the most recondite and most
complex operations of animal life--those of the nervous system, these of
late years have been shown to be--I do not say identical in any sense with
the electrical processes--but this has been shown, that they are in some
way or other associated with them; that is to say, that every amount of
nervous action is accompanied by a certain amount of electrical disturbance
in the particles of the nerves in which that nervous action is carried on.
In this way the nervous action is related to electricity in the same way
that heat is related to electricity; and the same sort of argument which
demonstrates the two latter to be related to one another shows that the
nervous forces are correlated to electricity; for the experiments of M.
Dubois Reymond and others have shown that whenever a nerve is in a state of
excitement, sending a message to the muscles or conveying an impression to
the brain, there is a disturbance of the electrical condition of that nerve
which does not exist at other times; and there are a number of other facts
and phenomena of that sort; so that we come to the broad conclusion that
not only as to living matter itself, but as to the forces that matter
exerts, there is a close relationship between the organic and the inorganic
world--the difference between them arising from the diverse combination and
disposition of identical forces, and not from any primary diversity, so far
as we can see.
I said just now that the horse eventually died and became converted into
the same inorganic substances from whence all but an inappreciable fraction
of its substance demonstrably originated, so that the actual wanderings of
matter are as remarkable as the transmigrations of the soul fabled by
Indian tradition. But before death has occurred, in the one sex or the
other, and in fact in both, certain products or parts of the organism have
been set free, certain parts of the organisms of the two sexes have come
into contact with one another, and from that conjunction, from that union
which then takes place, there results the formation of a new being. At
stated times the mare, from a particular part of the interior of her body,
called the ovary, gets rid of a minute particle of matter comparable in all
essential respects with that which we called a cell a little while since,
which cell contains a kind of nucleus in its centre, surrounded by a clear
space and by a viscid mass of protein substance (Fig. 2); and though it is
different in appearance from the eggs which we are mostly acquainted with,
it is really an egg. After a time this minute particle of matter, which may
only be a small fraction of a grain in weight, undergoes a series of
changes,--wonderful, complex changes. Finally, upon its surface there is
fashioned a little elevation, which afterwards becomes divided and marked
by a groove. The lateral boundaries of the groove extend upwards and
downwards, and at length give rise to a double tube. In the upper and
smaller tube the spinal marrow and brain are fashioned; in the lower, the
alimentary canal and heart; and at length two pairs of buds shoot out at
the sides of the body, and they are the rudiments of the limbs. In fact a
true drawing of a section of the embryo in this state would in all
essential respects resemble that diagram of a horse reduced to its simplest
expression, which I first placed before you (Fig. 1).
Slowly and gradually these changes take place. The whole of the body, at
first, can be broken up into "cells," which become in one place
metamorphosed into muscle,--in another place into gristle and bone,--in
another place into fibrous tissue,--and in another into hair; every part
becoming gradually and slowly fashioned, as if there were an artificer at
work in each of these complex structures that I have mentioned. This
embryo, as it is called, then passes into other conditions. I should tell
you that there is a time when the embryos of neither dog, nor horse, nor
porpoise, nor monkey, nor man, can be distinguished by any essential
feature one from the other; there is a time when they each and all of them
resemble this one of the dog. But as development advances, all the parts
acquire their speciality, till at length you have the embryo converted into
the form of the parent from which it started. So that you see, this living
animal, this horse, begins its existence as a minute particle of
nitrogenous matter, which, being supplied with nutriment (derived, as I
have shown, from the inorganic world), grows up according to the special
type and construction of its parents, works and undergoes a constant waste,
and that waste is made good by nutriment derived from the inorganic world;
the waste given off in this way being directly added to the inorganic
world. Eventually the animal itself dies, and, by the process of
decomposition, its whole body is returned to those conditions of inorganic
matter in which its substance originated.
This, then, is that which is true of every living form, from the lowest
plant to the highest animal--to man himself. You might define the life of
every one in exactly the same terms as those which I have now used; the
difference between the highest and the lowest being simply in the
complexity of the developmental changes, the variety of the structural
forms, and the diversity of the physiological functions which are exerted
by each.
If I were to take an oak tree, as a specimen of the plant world, I should
find that it originated in an acorn, which, too, commenced in a cell; the
acorn is placed in the ground, and it very speedily begins to absorb the
inorganic matters I have named, adds enormously to its bulk, and we can see
it, year after year, extending itself upward and downward, attracting and
appropriating to itself inorganic materials, which it vivifies, and
eventually, as it ripens, gives off its own proper acorns, which again run
the same course. But I need not multiply examples,--from the highest to the
lowest the essential features of life are the same as I have described in
each of these cases.
So much, then, for these particular features of the organic world, which
you can understand and comprehend, so long as you confine yourself to one
sort of living being, and study that only.
But, as you know, horses are not the only living creatures in the world;
and again, horses, like all other animals, have certain limits--are
confined to a certain area on the surface of the earth on which we
live,--and, as that is the simpler matter, I may take that first. In its
wild state, and before the discovery of America, when the natural state of
things was interfered with by the Spaniards, the horse was only to be found
in parts of the earth which are known to geographers as the Old World; that
is to say, you might meet with horses in Europe, Asia, or Africa; but there
were none in Australia, and there were none whatsoever in the whole
continent of America, from Labrador down to Cape Horn. This is an empirical
fact, and it is what is called, stated in the way I have given it you, the
"Geographical Distribution" of the horse.
Why horses should be found in Europe, Asia, and Africa, and not in America,
is not obvious; the explanation that the conditions of life in America are
unfavourable to their existence, and that, therefore, they had not been
created there, evidently does not apply; for when the invading Spaniards,
or our own yeomen farmers, conveyed horses to these countries for their own
use, they were found to thrive well and multiply very rapidly; and many are
even now running wild in those countries, and in a perfectly natural
condition. Now, suppose we were to do for every animal what we have here
done for the horse,--that is, to mark off and distinguish the particular
district or region to which each belonged; and supposing we tabulated all
these results, that would be called the Geographical Distribution of
animals, while a corresponding study of plants would yield as a result the
Geographical Distribution of plants.
I pass on from that now, as I merely wished to explain to you what I meant
by the use of the term "Geographical Distribution." As I said, there is
another aspect, and a much more important one, and that is, the relations
of the various animals to one another. The horse is a very well-defined
matter-of-fact sort of animal, and we are all pretty familiar with its
structure. I dare say it may have struck you, that it resembles very much
no other member of the animal kingdom, except perhaps the zebra or the ass.
But let me ask you to look along these diagrams. Here is the skeleton of
the horse, and here the skeleton of the dog. You will notice that we have
in the horse a skull, a backbone and ribs, shoulder-blades and
haunch-bones. In the fore-limb, one upper arm-bone, two fore arm-bones,
wrist-bones (wrongly called knee), and middle hand-bones, ending in the
three bones of a finger, the last of which is sheathed in the horny hoof of
the fore-foot: in the hind-limb, one thigh-bone, two leg-bones,
ankle-bones, and middle foot-bones, ending in the three bones of a toe, the
last of which is encased in the hoof of the hind-foot. Now turn to the
dog's skeleton. We find identically the same bones, but more of them, there
being more toes in each foot, and hence more toe-bones.
Well, that is a very curious thing! The fact is that the dog and the
horse--when one gets a look at them without the outward impediments of the
skin--are found to be made in very much the same sort of fashion. And if I
were to make a transverse section of the dog, I should find the same organs
that I have already shown you as forming parts of the horse. Well, here is
another skeleton--that of a kind of lemur--you see he has just the same
bones; and if I were to make a transverse section of it, it would be just
the same again. In your mind's eye turn him round, so as to put his
backbone in a position inclined obliquely upwards and forwards, just as in
the next three diagrams, which represent the skeletons of an orang, a
chimpanzee, and a gorilla, and you find you have no trouble in identifying
the bones throughout; and lastly turn to the end of the series, the diagram
representing a man's skeleton, and still you find no great structural
feature essentially altered. There are the same bones in the same
relations. From the horse we pass on and on, with gradual steps until we
arrive at last at the highest known forms. On the other hand, take the
other line of diagrams, and pass from the horse downwards in the scale to
this fish; and still, though the modifications are vastly greater, the
essential framework of the organisation remains unchanged. Here, for
instance, is a porpoise: here is its strong backbone, with the cavity
running through it, which contains the spinal cord; here are the ribs, here
the shoulder-blade; here is the little short upper-arm bone, here are the
two forearm bones, the wrist-bone, and the finger-bones.
Strange, is it not, that the porpoise should have in this queer-looking
affair--its flapper (as it is called), the same fundamental elements as the
fore-leg of the horse or the dog, or the ape or man; and here you will
notice a very curious thing,--the hinder limbs are absent. Now, let us make
another jump. Let us go to the codfish: here you see is the forearm, in
this large pectoral fin--carrying your mind's eye onward from the flapper
of the porpoise. And here you have the hinder limbs restored in the shape
of these ventral fins. If I were to make a transverse section of this, I
should find just the same organs that we have before noticed. So that, you
see, there comes out this strange conclusion as the result of our
investigations, that the horse, when examined and compared with other
animals, is found by no means to stand alone in Nature; but that there are
an enormous number of other creatures which have backbones, ribs, and legs,
and other parts arranged in the same general manner, and in all their
formation exhibiting the same broad peculiarities.
I am sure that you cannot have followed me even in this extremely
elementary exposition of the structural relations of animals, without
seeing what I have been driving at all through, which is, to show you that,
step by step, naturalists have come to the idea of a unity of plan, or
conformity of construction, among animals which appeared at first sight to
be extremely dissimilar.
And here you have evidence of such a unity of plan among all the animals
which have backbones, and which we technically call _Vertebrata_. But
there are multitudes of other animals, such as crabs, lobsters, spiders,
and so on, which we term _Annulosa_. In these I could not point out to
you the parts that correspond with those of the horse,--the backbone, for
instance,--as they are constructed upon a very different principle, which
is also common to all of them; that is to say, the lobster, the spider, and
the centipede, have a common plan running through their whole arrangement,
in just the same way that the horse, the dog, and the porpoise assimilate
to each other.
Yet other creatures--whelks, cuttlefishes, oysters, snails, and all their
tribe (_Mollusca_)--resemble one another in the same way, but differ
from both _Vertebrata_ and _Annulosa_; and the like is true of
the animals called _Coelenterata_ (Polypes) and _Protozoa_
(animalcules and sponges).
Now, by pursuing this sort of comparison, naturalists have arrived at the
conviction that there are,--some think five, and some seven,--but certainly
not more than the latter number--and perhaps it is simpler to assume
five--distinct plans or constructions in the whole of the animal world; and
that the hundreds of thousands of species of creatures on the surface of
the earth, are all reducible to those five, or, at most, seven, plans of
organisation.
But can we go no further than that? When one has got so far, one is tempted
to go on a step and inquire whether we cannot go back yet further and bring
down the whole to modifications of one primordial unit. The anatomist
cannot do this; but if he call to his aid the study of development, he can
do it. For we shall find that, distinct as those plans are, whether it be a
porpoise or man, or lobster, or any of those other kinds I have mentioned,
every one begins its existence with one and the same primitive form,--that
of the egg, consisting, as we have seen, of a nitrogenous substance, having
a small particle or nucleus in the centre of it. Furthermore, the earlier
changes of each are substantially the same. And it is in this that lies
that true "unity of organisation" of the animal kingdom which has been
guessed at and fancied for many years; but which it has been left to the
present time to be demonstrated by the careful study of development. But is
it possible to go another step further still, and to show that in the same
way the whole of the organic world is reducible to one primitive condition
of form? Is there among the plants the same primitive form of organisation,
and is that identical with that of the animal kingdom? The reply to that
question, too, is not uncertain or doubtful. It is now proved that every
plant begins its existence under the same form; that is to say, in that of
a cell--a particle of nitrogenous matter having substantially the same
conditions. So that if you trace back the oak to its first germ, or a man,
or a horse, or lobster, or oyster, or any other animal you choose to name,
you shall find each and all of these commencing their existence in forms
essentially similar to each other; and, furthermore, that the first
processes of growth, and many of the subsequent modifications, are
essentially the same in principle in almost all.
In conclusion, let me, in a few words, recapitulate the positions which I
have laid down. And you must understand that I have not been talking mere
theory; I have been speaking of matters which are as plainly demonstrable
as the commonest propositions of Euclid--of facts that must form the basis
of all speculations and beliefs in Biological science. We have gradually
traced down all organic forms, or, in other words, we have analysed the
present condition of animated nature, until we found that each species took
its origin in a form similar to that under which all the others commenced
their existence. We have found the whole of the vast array of living forms
with which we are surrounded, constantly growing, increasing, decaying and
disappearing; the animal constantly attracting, modifying, and applying to
its sustenance the matter of the vegetable kingdom, which derived its
support from the absorption and conversion of inorganic matter. And so
constant and universal is this absorption, waste, and reproduction, that it
may be said with perfect certainty that there is left in no one of our
bodies at the present moment a millionth part of the matter of which they
were originally formed! We have seen, again, that not only is the living
matter derived from the inorganic world, but that the forces of that matter
are all of them correlative with and convertible into those of inorganic
nature.
This, for our present purposes, is the best view of the present condition
of organic nature which I can lay before you: it gives you the great
outlines of a vast picture, which you must fill up by your own study.
In the next lecture I shall endeavour in the same way to go back into the
past, and to sketch in the same broad manner the history of life in epochs
preceding our own.
II. THE PAST CONDITION OF ORGANIC NATURE
In the lecture which I delivered last Monday evening, I endeavoured to
sketch in a very brief manner, but as well as the time at my disposal would
permit, the present condition of organic nature, meaning by that large
title simply an indication of the great, broad, and general principles
which are to be discovered by those who look attentively at the phenomena
of organic nature as at present displayed. The general result of our
investigations might be summed up thus: we found that the multiplicity of
the forms of animal life, great as that may be, may be reduced to a
comparatively few primitive plans or types of construction; that a further
study of the development of those different forms revealed to us that they
were again reducible, until we at last brought the infinite diversity of
animal, and even vegetable life, down to the primordial form of a single
cell.
We found that our analysis of the organic world, whether animals or plants,
showed, in the long run, that they might both be reduced into, and were, in
fact, composed of, the same constituents. And we saw that the plant
obtained the materials constituting its substance by a peculiar combination
of matters belonging entirely to the inorganic world; that, then, the
animal was constantly appropriating the nitrogenous matters of the plant to
its own nourishment, and returning them back to the inorganic world, in
what we spoke of as its waste; and that finally, when the animal ceased to
exist, the constituents of its body were dissolved and transmitted to that
inorganic world whence they had been at first abstracted. Thus we saw in
both the blade of grass and the horse but the same elements differently
combined and arranged. We discovered a continual circulation going on,--the
plant drawing in the elements of inorganic nature and combining them into
food for the animal creation; the animal borrowing from the plant the
matter for its own support, giving off during its life products which
returned immediately to the inorganic world; and that, eventually, the
constituent materials of the whole structure of both animals and plants
were thus returned to their original source: there was a constant passage
from one state of existence to another, and a returning back again.
Lastly, when we endeavoured to form some notion of the nature of the forces
exercised by living beings, we discovered that they--if not capable of
being subjected to the same minute analysis as the constituents of those
beings themselves--that they were correlative with--that they were the
equivalents of the forces of inorganic nature--that they were, in the sense
in which the term is now used, convertible with them. That was our general
result.
And now, leaving the Present, I must endeavour in the same manner to put
before you the facts that are to be discovered in the Past history of the
living world, in the past conditions of organic nature. We have, to-night,
to deal with the facts of that history--a history involving periods of time
before which our mere human records sink into utter insignificance--a
history the variety and physical magnitude of whose events cannot even be
foreshadowed by the history of human life and human phenomena--a history of
the most varied and complex character.
We must deal with the history, then, in the first place, as we should deal
with all other histories. The historical student knows that his first
business should be to inquire into the validity of his evidence, and the
nature of the record in which the evidence is contained, that he may be
able to form a proper estimate of the correctness of the conclusions which
have been drawn from that evidence. So, here we must pass, in the first
place, to the consideration of a matter which may seem foreign to the
question under discussion. We must dwell upon the nature of the records,
and the credibility of the evidence they contain; we must look to the
completeness or incompleteness of those records themselves, before we turn
to that which they contain and reveal. The question of the credibility of
the history, happily for us, will not require much consideration, for, in
this history, unlike those of human origin, there can be no cavilling, no
differences as to the reality and truth of the facts of which it is made
up; the facts state themselves, and are laid out clearly before us.
But, although one of the greatest difficulties of the historical student is
cleared out of our path, there are other difficulties--difficulties in
rightly interpreting the facts as they are presented to us--which may be
compared with the greatest difficulties of any other kinds of historical
study.
What is this record of the past history of the globe, and what are the
questions which are involved in an inquiry into its completeness or
incompleteness? That record is composed of mud; and the question which we
have to investigate this evening resolves itself into a question of the
formation of mud. You may think, perhaps, that this is a vast step--of
almost from the sublime to the ridiculous--from the contemplation of the
history of the past ages of the world's existence to the consideration of
the history of the formation of mud! But, in Nature, there is nothing mean
and unworthy of attention; there is nothing ridiculous or contemptible in
any of her works; and this inquiry, you will soon see, I hope, takes us to
the very root and foundations of our subject.
How, then, is mud formed? Always, with some trifling exceptions, which I
need not consider now--always, as the result of the action of water,
wearing down and disintegrating the surface of the earth and rocks with
which it comes in contact--pounding and grinding it down, and carrying the
particles away to places where they cease to be disturbed by this
mechanical action, and where they can subside and rest. For the ocean,
urged by winds, washes, as we know, a long extent of coast, and every wave,
loaded as it is with particles of sand and gravel as it breaks upon the
shore, does something towards the disintegrating process. And thus, slowly
but surely, the hardest rocks are gradually ground down to a powdery
substance; and the mud thus formed, coarser or finer, as the case may be,
is carried by the rush of the tides, or currents, till it reaches the
comparatively deeper parts of the ocean, in which it can sink to the
bottom, that is, to parts where there is a depth of about fourteen or
fifteen fathoms, a depth at which the water is, usually, nearly motionless,
and in which, of course, the finer particles of this detritus, or mud as we
call it, sinks to the bottom.
Or, again, if you take a river, rushing down from its mountain sources,
brawling over the stones and rocks that intersect its path, loosening,
removing, and carrying with it in its downward course the pebbles and
lighter matters from its banks, it crushes and pounds down the rocks and
earths in precisely the same way as the wearing action of the sea waves.
The matters forming the deposit are torn from the mountain-side and whirled
impetuously into the valley, more slowly over the plain, thence into the
estuary, and from the estuary they are swept into the sea. The coarser and
heavier fragments are obviously deposited first, that is, as soon as the
current begins to lose its force by becoming amalgamated with the stiller
depths of the ocean, but the finer and lighter particles are carried
further on, and eventually deposited in a deeper and stiller portion of the
ocean.
It clearly follows from this that mud gives us a chronology; for it is
evident that supposing this, which I now sketch, to be the sea bottom, and
supposing this to be a coast-line; from the washing action of the sea upon
the rock, wearing and grinding it down into a sediment of mud, the mud will
be carried down, and, at length, deposited in the deeper parts of this sea
bottom, where it will form a layer; and then, while that first layer is
hardening, other mud which is coming from the same source will, of course,
be carried to the same place; and, as it is quite impossible for it to get
beneath the layer already there, it deposits itself above it, and forms
another layer, and in that way you gradually have layers of mud constantly
forming and hardening one above the other, and conveying a record of time.
It is a necessary result of the operation of the law of gravitation that
the uppermost layer shall be the youngest and the lowest the oldest, and
that the different beds shall be older at any particular point or spot in
exactly the ratio of their depth from the surface. So that if they were
upheaved afterwards, and you had a series of these different layers of mud,
converted into sandstone, or limestone, as the case might be, you might be
sure that the bottom layer was deposited first, and that the upper layers
were formed afterwards. Here, you see, is the first step in the
history--these layers of mud give us an idea of time.
The whole surface of the earth,--I speak broadly, and leave out minor
qualifications,--is made up of such layers of mud, so hard, the majority of
them, that we call them rock whether limestone or sandstone, or other
varieties of rock. And, seeing that every part of the crust of the earth is
made up in this way, you might think that the determination of the
chronology, the fixing of the time which it has taken to form this crust is
a comparatively simple matter. Take a broad average, ascertain how fast the
mud is deposited upon the bottom of the sea, or in the estuary of rivers;
take it to be an inch, or two, or three inches a year, or whatever you may
roughly estimate it at; then take the total thickness of the whole series
of stratified rocks, which geologists estimate at twelve or thirteen miles,
or about seventy thousand feet, make a sum in short division, divide the
total thickness by that of the quantity deposited in one year, and the
result will, of course, give you the number of years which the crust has
taken to form.
Truly, that looks a very simple process! It would be so except for certain
difficulties, the very first of which is that of finding how rapidly
sediments are deposited; but the main difficulty--a difficulty which
renders any certain calculations of such a matter out of the question--is
this, the sea-bottom on which the deposit takes place is continually
shifting.
Instead of the surface of the earth being that stable, fixed thing that it
is popularly believed to be, being, in common parlance, the very emblem of
fixity itself, it is incessantly moving, and is, in fact, as unstable as
the surface of the sea, except that its undulations are infinitely slower
and enormously higher and deeper.
Now, what is the effect of this oscillation? Take the case to which I have
previously referred. The finer or coarser sediments that are carried down
by the current of the river, will only be carried out a certain distance,
and eventually, as we have already seen, on reaching the stiller part of
the ocean, will be deposited at the bottom.
[Illustration: Fig. 4.]
Let C _y_ (Fig. 4) be the sea-bottom, _y_ D the shore, _x y_
the sea-level, then the coarser deposit will subside over the region B, the
finer over A, while beyond A there will be no deposit at all; and,
consequently, no record will be kept, simply because no deposit is going
on. Now, suppose that the whole land, C, D, which we have regarded as
stationary, goes down, as it does so, both A and B go further out from the
shore, which will be at _y1_; _x1_, _y1_, being the new
sea-level. The consequence will be that the layer of mud (A), being now,
for the most part, further than the force of the current is strong enough
to convey even the finest _débris_, will, of course, receive no more
deposits, and having attained a certain thickness will now grow no thicker.
We should be misled in taking the thickness of that layer, whenever it may
be exposed to our view, as a record of time in the manner in which we are
now regarding this subject, as it would give us only an imperfect and
partial record: it would seem to represent too short a period of time.
Suppose, on the other hand, that the land (C D) had gone on rising slowly
and gradually--say an inch or two inches in the course of a century,--what
would be the practical effect of that movement? Why, that the sediment A
and B which has been already deposited, would eventually be brought nearer
to the shore-level and again subjected to the wear and tear of the sea; and
directly the sea begins to act upon it, it would of course soon cut up and
carry it way, to a greater or less extent, to be re-deposited further out.
Well, as there is, in all probability, not one single spot on the whole
surface of the earth, which has not been up and down in this way a great
many times, it follows that the thickness of the deposits formed at any
particular spot cannot be taken (even supposing we had at first obtained
correct data as to the rate at which they took place), as affording
reliable information as to the period of time occupied in its deposit. So
that you see it is absolutely necessary from these facts, seeing that our
record entirely consists of accumulations of mud, superimposed one on the
other; seeing in the next place that any particular spots on which
accumulations have occurred, have been constantly moving up and down, and
sometimes out of the reach of a deposit, and at other times its own deposit
broken up and carried away, it follows that our record must be in the
highest degree imperfect, and we have hardly a trace left of thick
deposits, or any definite knowledge of the area that they occupied, in a
great many cases. And mark this! That supposing even that the whole surface
of the earth had been accessible to the geologist,--that man had had access
to every part of the earth, and had made sections of the whole, and put
them all together,--even then his record must of necessity be imperfect.
But to how much has man really access? If you will look at this map you
will see that it represents the proportion of the sea to the earth: this
coloured part indicates all the dry land, and this other portion is the
water. You will notice at once that the water covers three-fifths of the
whole surface of the globe, and has covered it in the same manner ever
since man has kept any record of his own observations, to say nothing of
the minute period during which he has cultivated geological inquiry. So
that three-fifths of the surface of the earth is shut out from us because
it is under the sea. Let us look at the other two-fifths, and see what are
the countries in which anything that may be termed searching geological
inquiry has been carried out: a good deal of France, Germany, and Great
Britain and Ireland, bits of Spain, of Italy, and of Russia, have been
examined, but of the whole great mass of Africa, except parts of the
southern extremity, we know next to nothing; little bits of India, but of
the greater part of the Asiatic continent nothing; bits of the Northern
American States and of Canada, but of the greater part of the continent of
North America, and in still larger proportion, of South America, nothing!
Under these circumstances, it follows that even with reference to that kind
of imperfect information which we can possess, it is only of about the
ten-thousandth part of the accessible parts of the earth that has been
examined properly. Therefore, it is with justice that the most thoughtful
of those who are concerned in these inquiries insist continually upon the
imperfection of the geological record; for, I repeat, it is absolutely
necessary, from the nature of things, that that record should be of the
most fragmentary and imperfect character. Unfortunately this circumstance
has been constantly forgotten. Men of science, like young colts in a fresh
pasture, are apt to be exhilarated on being turned into a new field of
inquiry, to go off at a hand-gallop, in total disregard of hedges and
ditches, to lose sight of the real limitation of their inquiries, and to
forget the extreme imperfection of what is really known. Geologists have
imagined that they could tell us what was going on at all parts of the
earth's surface during a given epoch; they have talked of this deposit
being contemporaneous with that deposit, until, from our little local
histories of the changes at limited spots of the earth's surface, they have
constructed a universal history of the globe as full of wonders and
portents as any other story of antiquity.
But what does this attempt to construct a universal history of the globe
imply? It implies that we shall not only have a precise knowledge of the
events which have occurred at any particular point, but that we shall be
able to say what events, at any one spot, took place at the same time with
those at other spots.
Let us see how far that is in the nature of things practicable. Suppose
that here I make a section of the Lake of Killarney, and here the section
of another lake--that of Loch Lomond in Scotland for instance. The rivers
that flow into them are constantly carrying down deposits of mud, and beds,
or strata, are being as constantly formed, one above the other, at the
bottom of those lakes. Now, there is not a shadow of doubt that in these
two lakes the lower beds are all older than the upper--there is no doubt
about that; but what does _this_ tell us about the age of any given
bed in Loch Lomond, as compared with that of any given bed in the Lake of
Killarney? It is, indeed, obvious that if any two sets of deposits are
separated and discontinuous, there is absolutely no means whatever given
you by the nature of the deposit of saying whether one is much younger or
older than the other; but you may say, as many have said and think, that
the case is very much altered if the beds which we are comparing are
continuous. Suppose two beds of mud hardened into rock,--A and B--are seen
in section. (Fig. 5.)
[Illustration: Fig. 5.]
Well, you say, it is admitted that the lowermost bed is always the older.
Very well; B, therefore, is older than A. No doubt, _as a whole_, it
is so; or if any parts of the two beds which are in the same vertical line
are compared, it is so. But suppose you take what seems a very natural step
further, and say that the part _a_ of the bed A is younger than the
part _b_ of the bed B. Is this sound reasoning? If you find any record
of changes taking place at _b_, did they occur before any events which
took place while _a_ was being deposited? It looks all very plain
sailing, indeed, to say that they did; and yet there is no proof of
anything of the kind. As the former Director of this Institution, Sir H. De
la Beche, long ago showed, this reasoning may involve an entire fallacy. It
is extremely possible that _a_ may have been deposited ages before
_b_. It is very easy to understand how that can be. To return to Fig.
4; when A and B were deposited, they were _substantially_
contemporaneous; A being simply the finer deposit, and B the coarser of the
same detritus or waste of land. Now suppose that that sea-bottom goes down
(as shown in Fig. 4), so that the first deposit is carried no farther than
_a_, forming the bed A1, and the coarse no farther than _b_,
forming the bed B1, the result will be the formation of two continuous
beds, one of fine sediment (A A1) over-lapping another of coarse sediment
(B B1). Now suppose the whole sea-bottom is raised up, and a section
exposed about the point A1; no doubt, _at this spot_, the upper bed is
younger than the lower. But we should obviously greatly err if we concluded
that the mass of the upper bed at A was younger than the lower bed at B;
for we have just seen that they are contemporaneous deposits. Still more
should we be in error if we supposed the upper bed at A to be younger than
the continuation of the lower bed at B1; for A was deposited long before
B1. In fine, if, instead of comparing immediately adjacent parts of two
beds, one of which lies upon another, we compare distant parts, it is quite
possible that the upper may be any number of years older than the under,
and the under any number of years younger than the upper.
Now you must not suppose that I put this before you for the purpose of
raising a paradoxical difficulty; the fact is, that the great mass of
deposits have taken place in sea-bottoms which are gradually sinking, and
have been formed under the very conditions I am here supposing.
Do not run away with the notion that this subverts the principle I laid
down at first. The error lies in extending a principle which is perfectly
applicable to deposits in the same vertical line to deposits which are not
in that relation to one another.
It is in consequence of circumstances of this kind, and of others that I
might mention to you, that our conclusions on and interpretations of the
record are really and strictly only valid so long as we confine ourselves
to one vertical section. I do not mean to tell you that there are no
qualifying circumstances, so that, even in very considerable areas, we may
safely speak of conformably superimposed beds being older or younger than
others at many different points. But we can never be quite sure in coming
to that conclusion, and especially we cannot be sure if there is any break
in their continuity, or any very great distance between the points to be
compared.
Well now, so much for the record itself,--so much for its
imperfections,--so much for the conditions to be observed in interpreting
it, and its chronological indications, the moment we pass beyond the limits
of a vertical linear section.
Now let us pass from the record to that which it contains,--from the book
itself to the writing and the figures on its pages. This writing and these
figures consist of remains of animals and plants which, in the great
majority of cases, have lived and died in the very spot in which we now
find them, or at least in the immediate vicinity. You must all of you be
aware--and I referred to the fact in my last lecture--that there are vast
numbers of creatures living at the bottom of the sea. These creatures, like
all others, sooner or later die, and their shells and hard parts lie at the
bottom; and then the fine mud which is being constantly brought down by
rivers and the action of the wear and tear of the sea, covers them over and
protects them from any further change or alteration; and, of course, as in
process of time the mud becomes hardened and solidified, the shells of
these animals are preserved and firmly imbedded in the limestone or
sandstone which is being thus formed. You may see in the galleries of the
Museum up stairs specimens of limestones in which such fossil remains of
existing animals are imbedded. There are some specimens in which turtles'
eggs have been imbedded in calcareous sand, and before the sun had hatched
the young turtles, they became covered over with calcareous mud, and thus
have been preserved and fossilised.
Not only does this process of imbedding and fossilisation occur with marine
and other aquatic animals and plants, but it affects those land animals and
plants which are drifted away to sea, or become buried in bogs or morasses;
and the animals which have been trodden down by their fellows and crushed
in the mud at the river's bank, as the herd have come to drink. In any of
these cases, the organisms may be crushed or be mutilated, before or after
putrefaction, in such a manner that perhaps only a part will be left in the
form in which it reaches us. It is, indeed, a most remarkable fact, that it
is quite an exceptional case to find a skeleton of any one of all the
thousands of wild land animals that we know are constantly being killed, or
dying in the course of nature: they are preyed on and devoured by other
animals, or die in places where their bodies are not afterwards protected
by mud. There are other animals existing on the sea, the shells of which
form exceedingly large deposits. You are probably aware that before the
attempt was made to lay the Atlantic telegraphic cable, the Government
employed vessels in making a series of very careful observations and
soundings of the bottom of the Atlantic; and although, as we must all
regret, that up to the present time that project has not succeeded, we have
the satisfaction of knowing that it yielded some most remarkable results to
science. The Atlantic Ocean had to be sounded right across, to depths of
several miles in some places, and the nature of its bottom was carefully
ascertained. Well, now, a space of about 1,000 miles wide from east to
west, and I do not exactly know how many from north to south, but at any
rate 600 or 700 miles, was carefully examined, and it was found that over
the whole of that immense area an excessively fine chalky mud is being
deposited; and this deposit is entirely made up of animals whose hard parts
are deposited in this part of the ocean, and are doubtless gradually
acquiring solidity and becoming metamorphosed into a chalky limestone.
Thus, you see, it is quite possible in this way to preserve unmistakable
records of animal and vegetable life. Whenever the sea-bottom, by some of
those undulations of the earth's crust that I have referred to, becomes
up-heaved, and sections or borings are made, or pits are dug, then we
become able to examine the contents and constituents of these ancient
sea-bottoms, and find out what manner of animals lived at that period.
Now it is a very important consideration in its bearing on the completeness
of the record, to inquire how far the remains contained in these
fossiliferous limestones are able to convey anything like an accurate or
complete account of the animals which were in existence at the time of its
formation. Upon that point we can form a very clear judgment, and one in
which there is no possible room for any mistake. There are of course a
great number of animals--such as jellyfishes, and other animals--without
any hard parts, of which we cannot reasonably expect to find any traces
whatever: there is nothing of them to preserve. Within a very short time,
you will have noticed, after they are removed from the water, they dry up
to a mere nothing; certainly they are not of a nature to leave any very
visible traces of their existence on such bodies as chalk or mud. Then
again, look at land animals; it is, as I have said, a very uncommon thing
to find a land animal entire after death. Insects and other carnivorous
animals very speedily pull them to pieces, putrefaction takes place, and
so, out of the hundreds of thousands that are known to die every year, it
is the rarest thing in the world to see one imbedded in such a way that its
remains would be preserved for a lengthened period. Not only is this the
case, but even when animal remains have been safely imbedded, certain
natural agents may wholly destroy and remove them.
Almost all the hard parts of animals--the bones and so on--are composed
chiefly of phosphate of lime and carbonate of lime. Some years ago, I had
to make an inquiry into the nature of some very curious fossils sent to me
from the North of Scotland. Fossils are usually hard bony structures that
have become imbedded in the way I have described, and have gradually
acquired the nature and solidity of the body with which they are
associated; but in this case I had a series of _holes_ in some pieces
of rock, and nothing else. Those holes, however, had a certain definite
shape about them, and when I got a skilful workman to make castings of the
interior of these holes, I found that they were the impressions of the
joints of a backbone and of the armour of a great reptile, twelve or more
feet long. This great beast had died and got buried in the sand; the sand
had gradually hardened over the bones, but remained porous. Water had
trickled through it, and that water being probably charged with a
superfluity of carbonic acid, had dissolved all the phosphate and carbonate
of lime, and the bones themselves had thus decayed and entirely
disappeared; but as the sandstone happened to have consolidated by that
time, the precise shape of the bones was retained. If that sandstone had
remained soft a little longer, we should have known nothing whatsoever of
the existence of the reptile whose bones it had encased.
How certain it is that a vast number of animals which have existed at one
period on this earth have entirely perished, and left no trace whatever of
their forms, may be proved to you by other considerations. There are large
tracts of sandstone in various parts of the world, in which nobody has yet
found anything but footsteps. Not a bone of any description, but an
enormous number of traces of footsteps. There is no question about them.
There is a whole valley in Connecticut covered with these footsteps, and
not a single fragment of the animals which made them have yet been found.
Let me mention another case while upon that matter, which is even more
surprising than those to which I have yet referred. There is a limestone
formation near Oxford, at a place called Stonesfield, which has yielded the
remains of certain very interesting mammalian animals, and up to this time,
if I recollect rightly, there have been found seven specimens of its lower
jaws, and not a bit of anything else, neither limb-bones nor skull, nor any
part whatever; not a fragment of the whole system! Of course, it would be
preposterous to imagine that the beasts had nothing else but a lower jaw!
The probability is, as Dr. Buckland showed, as the result of his
observations on dead dogs in the river Thames, that the lower jaw, not
being secured by very firm ligaments to the bones of the head, and being a
weighty affair, would easily be knocked off, or might drop away from the
body as it floated in water in a state of decomposition. The jaw would thus
be deposited immediately, while the rest of the body would float and drift
away altogether, ultimately reaching the sea, and perhaps becoming
destroyed. The jaw becomes covered up and preserved in the river silt, and
thus it comes that we have such a curious circumstance as that of the lower
jaws in the Stonesfield slates. So that, you see, faulty as these layers of
stone in the earth's crust are, defective as they necessarily are as a
record, the account of contemporaneous vital phenomena presented by them
is, by the necessity of the case, infinitely more defective and
fragmentary.
It was necessary that I should put all this very strongly before you,
because, otherwise, you might have been led to think differently of the
completeness of our knowledge by the next facts I shall state to you.
The researches of the last three-quarters of a century have, in truth,
revealed a wonderful richness of organic life in those rocks. Certainly not
fewer than thirty or forty thousand different species of fossils have been
discovered. You have no more ground for doubting that these creatures
really lived and died at or near the places in which we find them than you
have for like scepticism about a shell on the sea-shore. The evidence is as
good in the one case as in the other.
Our next business is to look at the general character of these fossil
remains, and it is a subject which will be requisite to consider carefully;
and the first point for us is to examine how much the extinct _Flora_
and _Fauna_ as a _whole_--disregarding altogether the
_succession_ of their constituents, of which I shall speak
afterwards--differ from the _Flora_ and _Fauna_ of the present
day;--how far they differ in what we _do_ know about them, leaving
altogether out of consideration speculations based upon what we _do
not_ know.
I strongly imagine that if it were not for the peculiar appearance that
fossilised animals have, any of you might readily walk through a museum
which contains fossil remains mixed up with those of the present forms of
life, and I doubt very much whether your uninstructed eyes would lead you
to see any vast or wonderful difference between the two. If you looked
closely, you would notice, in the first place, a great many things very
like animals with which you are acquainted now: you would see differences
of shape and proportion, but on the whole a close similarity.
I explained what I meant by ORDERS the other day, when I described the
animal kingdom as being divided into sub-kingdoms, classes and orders. If
you divide the animal kingdom into orders you will find that there are
above one hundred and twenty. The number may vary on one side or the other,
but this is a fair estimate. That is the sum total of the orders of all the
animals which we know now, and which have been known in past times, and
left remains behind.
Now, how many of those are absolutely extinct? That is to say, how many of
these orders of animals have lived at a former period of the world's
history but have at present no representatives? That is the sense in which
I meant to use the word "extinct." I mean that those animals did live on
this earth at one time, but have left no one of their kind with us at the
present moment. So that estimating the number of extinct animals is a sort
of way of comparing the past creation as a whole with the present as a
whole. Among the mammalia and birds there are none extinct; but when we
come to the reptiles there is a most wonderful thing: out of the eight
orders, or thereabouts, which you can make among reptiles, one-half are
extinct. These diagrams of the plesiosaurus, the ichthyosaurus, the
pterodactyle, give you a notion of some of these extinct reptiles. And here
is a cast of the pterodactyle and bones of the ichthyosaurus and the
plesiosaurus, just as fresh-looking as if it had been recently dug up in a
churchyard. Thus, in the reptile class, there are no less than half of the
orders which are absolutely extinct. If we turn to the _Amphibia_,
there was one extinct order, the Labyrinthodonts, typified by the large
salamander-like beast shown in this diagram.
No order of fishes is known to be extinct. Every fish that we find in the
strata--to which I have been referring--can be identified and placed in one
of the orders which exist at the present day. There is not known to be a
single ordinal form of insect extinct. There are only two orders extinct
among the _Crustacea_. There is not known to be an extinct order of
these creatures, the parasitic and other worms; but there are two, not to
say three, absolutely extinct orders of this class, the
_Echinodermata_; out of all the orders of the _Coelenterata_ and
_Protozoa_ only one, the Rugose Corals.
So that, you see, out of somewhere about 120 orders of animals, taking them
altogether, you will not, at the outside estimate, find above ten or a
dozen extinct. Summing up all the order of animals which have left remains
behind them, you will not find above ten or a dozen which cannot be
arranged with those of the present day; that is to say, that the difference
does not amount to much more than ten per cent.: and the proportion of
extinct orders of plants is still smaller. I think that that is a very
astounding a most astonishing fact: seeing the enormous epochs of time
which have elapsed during the constitution of the surface of the earth as
it at present exists, it is, indeed, a most astounding thing that the
proportion of extinct ordinal types should be so exceedingly small.
But now, there is another point of view in which we must look at this past
creation. Suppose that we were to sink a vertical pit through the floor
beneath us, and that I could succeed in making a section right through in
the direction of New Zealand, I should find in each of the different beds
through which I passed the remains of animals which I should find in that
stratum and not in the others. First, I should come upon beds of gravel or
drift containing the bones of large animals, such as the elephant,
rhinoceros, and cave tiger. Rather curious things to fall across in
Piccadilly! If I should dig lower still, I should come upon a bed of what
we call the London clay, and in this, as you will see in our galleries up
stairs, are found remains of strange cattle, remains of turtles, palms, and
large tropical fruits; with shell-fish such as you see the like of now only
in tropical regions. If I went below that, I should come upon the chalk,
and there I should find something altogether different, the remains of
ichthyosauria and pterodactyles, and ammonites, and so forth.
I do not know what Mr. Godwin Austin would say comes next, but probably
rocks containing more ammonites, and more ichthyosauria and plesiosauria,
with a vast number of other things; and under that I should meet with yet
older rocks containing numbers of strange shells and fishes; and in thus
passing from the surface to the lowest depths of the earth's crust, the
forms of animal life and vegetable life which I should meet with in the
successive beds would, looking at them broadly, be the more different the
further that I went down. Or, in other words, inasmuch as we started with
the clear principle, that in a series of naturally-disposed mud beds the
lowest are the oldest, we should come to this result, that the further we
go back in time the more difference exists between the animal and vegetable
life of an epoch and that which now exists. That was the conclusion to
which I wished to bring you at the end of this lecture.
III. THE METHOD BY WHICH THE CAUSES OF THE PRESENT AND PAST CONDITIONS OF
ORGANIC NATURE ARE TO BE DISCOVERED;--THE ORIGINATION OF LIVING BEINGS
In the two preceding lectures I have endeavoured to indicate to you the
extent of the subject-matter of the inquiry upon which we are engaged; and
having thus acquired some conception of the past and present phenomena of
organic nature, I must now turn to that which constitutes the great problem
which we have set before ourselves;--I mean, the question of what knowledge
we have of the causes of these phenomena of organic nature, and how such
knowledge is obtainable.
Here, on the threshold of the inquiry, an objection meets us. There are in
the world a number of extremely worthy, well-meaning persons, whose
judgments and opinions are entitled to the utmost respect on account of
their sincerity, who are of opinion that vital phenomena, and especially
all questions relating to the origin of vital phenomena, are questions
quite apart from the ordinary run of inquiry, and are, by their very
nature, placed out of our reach. They say that all these phenomena
originated miraculously, or in some way totally different from the ordinary
course of nature, and that therefore they conceive it to be futile, not to
say presumptuous, to attempt to inquire into them.
To such sincere and earnest persons, I would only say, that a question of
this kind is not to be shelved upon theoretical or speculative grounds. You
may remember the story of the Sophist who demonstrated to Diogenes in the
most complete and satisfactory manner that he could not walk; that, in
fact, all motion was an impossibility; and that Diogenes refuted him by
simply getting up and walking round his tub. So, in the same way, the man
of science replies to objections of this kind, by simply getting up and
walking onward, and showing what science has done and is doing---by
pointing to that immense mass of facts which have been ascertained as
systematised under the forms of the great doctrines of morphology, of
development, of distribution, and the like. He sees an enormous mass of
facts and laws relating to organic beings, which stand on the same good
sound foundation as every other natural law. With this mass of facts and
laws before us, therefore, seeing that, as far as organic matters have
hitherto been accessible and studied, they have shown themselves capable of
yielding to scientific investigation, we may accept this as proof that
order and law reign there as well as in the rest of Nature. The man of
science says nothing to objectors of this sort, but supposes that we can
and shall walk to a knowledge of the origin of organic nature, in the same
way that we have walked to a knowledge of the laws and principles of the
inorganic world.
But there are objectors who say the same from ignorance and ill-will. To
such I would reply that the objection comes ill from them, and that the
real presumption, I may almost say the real blasphemy, in this matter, is
in the attempt to limit that inquiry into the causes of phenomena, which is
the source of all human blessings, and from which has sprung all human
prosperity and progress; for, after all, we can accomplish comparatively
little; the limited range of our own faculties bounds us on every
side,--the field of our powers of observation is small enough, and he who
endeavours to narrow the sphere of our inquiries is only pursuing a course
that is likely to produce the greatest harm to his fellow-men.
But now, assuming, as we all do, I hope, that these phenomena are properly
accessible to inquiry, and setting out upon our search into the causes of
the phenomena of organic nature, or at any rate, setting out to discover
how much we at present know upon these abstruse matters, the question
arises as to what is to be our course of proceeding, and what method we
must lay down for our guidance. I reply to that question, that our method
must be exactly the same as that which is pursued in any other scientific
inquiry, the method of scientific investigation being the same for all
orders of facts and phenomena whatsoever.
I must dwell a little on this point, for I wish you to leave this room with
a very clear conviction that scientific investigation is not, as many
people seem to suppose, some kind of modern black art. I say that you might
easily gather this impression from the manner in which many persons speak
of scientific inquiry, or talk about inductive and deductive philosophy, or
the principles of the "Baconian philosophy." I do protest that, of the vast
number of cants in this world, there are none, to my mind, so contemptible
as the pseudo-scientific cant which is talked about the "Baconian
philosophy."
To hear people talk about the great Chancellor--and a very great man he
certainly was,--you would think that it was he who had invented science,
and that there was no such thing as sound reasoning before the time of
Queen Elizabeth! Of course you say, that cannot possibly be true; you
perceive, on a moment's reflection, that such an idea is absurdly wrong,
and yet, so firmly rooted is this sort of impression,--I cannot call it an
idea, or conception,--the thing is too absurd to be entertained,--but so
completely does it exist at the bottom of most men's minds, that this has
been a matter of observation with me for many years past. There are many
men who, though knowing absolutely nothing of the subject with which they
may be dealing, wish, nevertheless, to damage the author of some view with
which they think fit to disagree. What they do, then, is not to go and
learn something about the subject, which one would naturally think the best
way of fairly dealing with it; but they abuse the originator of the view
they question, in a general manner, and wind up by saying that, "After all,
you know, the principles and method of this author are totally opposed to
the canons of the Baconian philosophy." Then everybody applauds, as a
matter of course, and agrees that it must be so. But if you were to stop
them all in the middle of their applause, you would probably find that
neither the speaker nor his applauders could tell you how or in what way it
was so; neither the one nor the other having the slightest idea of what
they mean when they speak of the "Baconian philosophy."
You will understand, I hope, that I have not the slightest desire to join
in the outcry against either the morals, the intellect, or the great genius
of Lord Chancellor Bacon. He was undoubtedly a very great man, let people
say what they will of him; but notwithstanding all that he did for
philosophy, it would be entirely wrong to suppose that the methods of
modern scientific inquiry originated with him, or with his age; they
originated with the first man, whoever he was; and indeed existed long
before him, for many of the essential processes of reasoning are exerted by
the higher order of brutes as completely and effectively as by ourselves.
We see in many of the brute creation the exercise of one, at least, of the
same powers of reasoning as that which we ourselves employ.
The method of scientific investigation is nothing but the expression of the
necessary mode of working of the human mind. It is simply the mode at which
all phenomena are reasoned about, rendered precise and exact. There is no
more difference, but there is just the same kind of difference, between the
mental operations of a man of science and those of an ordinary person, as
there is between the operations and methods of a baker or of a butcher
weighing out his goods in common scales, and the operations of a chemist in
performing a difficult and complex analysis by means of his balance and
finely-graduated weights. It is not that the action of the scales in the
one case, and the balance in the other, differ in the principles of their
construction or manner of working; but the beam of one is set on an
infinitely finer axis than the other, and of course turns by the addition
of a much smaller weight.
You will understand this better, perhaps, if I give you some familiar
example. You have all heard it repeated, I dare say, that men of science
work by means of induction and deduction, and that by the help of these
operations, they, in a sort of sense, wring from Nature certain other
things, which are called natural laws, and causes, and that out of these,
by some cunning skill of their own, they build up hypotheses and theories.
And it is imagined by many, that the operations of the common mind can be
by no means compared with these processes, and that they have to be
acquired by a sort of special apprenticeship to the craft. To hear all
these large words, you would think that the mind of a man of science must
be constituted differently from that of his fellow men; but if you will not
be frightened by terms, you will discover that you are quite wrong, and
that all these terrible apparatus are being used by yourselves every day
and every hour of your lives.
There is a well-known incident in one of Molière's plays, where the author
makes the hero express unbounded delight on being told that he had been
talking prose during the whole of his life. In the same way, I trust, that
you will take comfort, and be delighted with yourselves, on the discovery
that you have been acting on the principles of inductive and deductive
philosophy during the same period. Probably there is not one here who has
not in the course of the day had occasion to set in motion a complex train
of reasoning, of the very same kind, though differing of course in degree,
as that which a scientific man goes through in tracing the causes of
natural phenomena.
A very trivial circumstance will serve to exemplify this. Suppose you go
into a fruiterer's shop, wanting an apple,--you take up one, and, on biting
it, you find it is sour; you look at it, and see that it is hard and green.
You take up another one, and that too is hard, green, and sour. The shopman
offers you a third; but, before biting it, you examine it, and find that it
is hard and green, and you immediately say that you will not have it, as it
must be sour, like those that you have already tried.
Nothing can be more simple than that, you think; but if you will take the
trouble to analyse and trace out into its logical elements what has been
done by the mind, you will be greatly surprised. In the first place, you
have performed the operation of induction. You found that, in two
experiences, hardness and greenness in apples went together with sourness.
It was so in the first case, and it was confirmed by the second. True, it
is a very small basis, but still it is enough to make an induction from;
you generalise the facts, and you expect to find sourness in apples where
you get hardness and greenness. You found upon that a general law, that all
hard and green apples are sour; and that, so far as it goes, is a perfect
induction. Well, having got your natural law in this way, when you are
offered another apple which you find is hard and green, you say, "All hard
and green apples are sour; this apple is hard and green, therefore this
apple is sour." That train of reasoning is what logicians call a syllogism,
and has all its various parts and terms,--its major premiss, its minor
premiss, and its conclusion. And, by the help of further reasoning, which,
if drawn out, would have to be exhibited in two or three other syllogisms,
you arrive at your final determination, "I will not have that apple." So
that, you see, you have, in the first place, established a law by
induction, and upon that you have founded a deduction, and reasoned out the
special conclusion of the particular case. Well now, suppose, having got
your law, that at some time afterwards, you are discussing the qualities of
apples with a friend: you will say to him, "It is a very curious
thing,--but I find that all hard and green apples are sour!" Your friend
says to you, "But how do you know that?" You at once reply, "Oh, because I
have tried them over and over again, and have always found them to be so."
Well, if we were talking science instead of common sense, we should call
that an experimental verification. And, if still opposed, you go further,
and say, "I have heard from the people in Somersetshire and Devonshire,
where a large number of apples are grown, that they have observed the same
thing. It is also found to be the case in Normandy, and in North America.
In short, I find it to be the universal experience of mankind wherever
attention has been directed to the subject." Whereupon, your friend, unless
he is a very unreasonable man, agrees with you, and is convinced that you
are quite right in the conclusion you have drawn. He believes, although
perhaps he does not know he believes it, that the more extensive
verifications are,--that the more frequently experiments have been made,
and results of the same kind arrived at,--that the more varied the
conditions under which the same results are attained, the more certain is
the ultimate conclusion, and he disputes the question no further. He sees
that the experiment has been tried under all sorts of conditions, as to
time, place, and people, with the same result; and he says with you,
therefore, that the law you have laid down must be a good one, and he must
believe it.
In science we do the same thing;--the philosopher exercises precisely the
same faculties, though in a much more delicate manner. In scientific
inquiry it becomes a matter of duty to expose a supposed law to every
possible kind of verification, and to take care, moreover, that this is
done intentionally, and not left to a mere accident, as in the case of the
apples. And in science, as in common life, our confidence in a law is in
exact proportion to the absence, of variation in the result of our
experimental verifications. For instance, if you let go your grasp of an
article you may have in your hand, it will immediately fall to the ground.
That is a very common verification of one of the best established laws of
nature--that of gravitation. The method by which men of science establish
the existence of that law is exactly the same as that by which we have
established the trivial proposition about the sourness of hard and green
apples. But we believe it in such an extensive, thorough, and unhesitating
manner because the universal experience of mankind verifies it, and we can
verify it ourselves at any time; and that is the strongest possible
foundation on which any natural law can rest.
So much, then, by way of proof that the method of establishing laws in
science is exactly the same as that pursued in common life. Let us now turn
to another matter (though really it is but another phase of the same
question), and that is, the method by which, from the relations of certain
phenomena, we prove that some stand in the position of causes towards the
others.
I want to put the case clearly before you, and I will therefore show you
what I mean by another familiar example. I will suppose that one of you, on
coming down in the morning to the parlour of your house, finds that a
tea-pot and some spoons which had been left in the room on the previous
evening are gone,--the window is open, and you observe the mark of a dirty
hand on the window-frame, and perhaps, in addition to that, you notice the
impress of a hob-nailed shoe on the gravel outside. All these phenomena
have struck your attention instantly, and before two seconds have passed
you say, "Oh, somebody has broken open the window, entered the room, and
run off with the spoons and the tea-pot!" That speech is out of your mouth
in a moment. And you will probably add, "I know there has; I am quite sure
of it!" You mean to say exactly what you know; but in reality you are
giving expression to what is, in all essential particulars, an hypothesis.
You do not _know_ it at all; it is nothing but an hypothesis rapidly
framed in your own mind. And it is an hypothesis founded on a long train of
inductions and deductions.
What are those inductions and deductions, and how have you got at this
hypothesis? You have observed, in the first place, that the window is open;
but by a train of reasoning involving many inductions and deductions, you
have probably arrived long before at the general law--and a very good one
it is--that windows do not open of themselves; and you therefore conclude
that something has opened the window. A second general law that you have
arrived at in the same way is, that tea-pots and spoons do not go out of a
window spontaneously, and you are satisfied that, as they are not now where
you left them, they have been removed. In the third place, you look at the
marks on the window-sill, and the shoe-marks outside, and you say that in
all previous experience the former kind of mark has never been produced by
anything else but the hand of a human being; and the same experience shows
that no other animal but man at present wears shoes with hob-nails in them
such as would produce the marks in the gravel. I do not know, even if we
could discover any of those "missing links" that are talked about, that
they would help us to any other conclusion! At any rate the law which
states our present experience is strong enough for my present purpose. You
next reach the conclusion, that as these kinds of marks have not been left
by any other animals than men, or are liable to be formed in any other way
than by a man's hand and shoe, the marks in question have been formed by a
man in that way. You have, further, a general law, founded on observation
and experience, and that, too, is, I am sorry to say, a very universal and
unimpeachable one,--that some men are thieves; and you assume at once from
all these premisses--and that is what constitutes your hypothesis--that the
man who made the marks outside and on the window-sill, opened the window,
got into the room, and stole your tea-pot and spoons. You have now arrived
at a _vera causa_;--you have assumed a cause which, it is plain, is
competent to produce all the phenomena you have observed. You can explain
all these phenomena only by the hypothesis of a thief. But that is a
hypothetical conclusion, of the justice of which you have no absolute proof
at all; it is only rendered highly probable by a series of inductive and
deductive reasonings.
I suppose your first action, assuming that you are a man of ordinary common
sense, and that you have established this hypothesis to your own
satisfaction, will very likely be to go off for the police, and set them on
the track of the burglar, with the view to the recovery of your property.
But just as you are starting with this object, some person comes in, and on
learning what you are about, says, "My good friend, you are going on a
great deal too fast. How do you know that the man who really made the marks
took the spoons? It might have been a monkey that took them, and the man
may have merely looked in afterwards." You would probably reply, "Well,
that is all very well, but you see it is contrary to all experience of the
way tea-pots and spoons are abstracted; so that, at any rate, your
hypothesis is less probable than mine." While you are talking the thing
over in this way, another friend arrives, one of that good kind of people
that I was talking of a little while ago. And he might say, "Oh, my dear
sir, you are certainly going on a great deal too fast. You are most
presumptuous. You admit that all these occurrences took place when you were
fast asleep, at a time when you could not possibly have known anything
about what was taking place. How do you know that the laws of Nature are
not suspended during the night? It may be that there has been some kind of
supernatural interference in this case." In point of fact, he declares that
your hypothesis is one of which you cannot at all demonstrate the truth,
and that you are by no means sure that the laws of Nature are the same when
you are asleep as when you are awake.
Well, now, you cannot at the moment answer that kind of reasoning. You feel
that your worthy friend has you somewhat at a disadvantage. You will feel
perfectly convinced in your own mind, however, that you are quite right,
and you say to him, "My good friend, I can only be guided by the natural
probabilities of the case, and if you will be kind enough to stand aside
and permit me to pass, I will go and fetch the police." Well, we will
suppose that your journey is successful, and that by good luck you meet
with a policeman; that eventually the burglar is found with your property
on his person, and the marks correspond to his hand and to his boots.
Probably any jury would consider those facts a very good experimental
verification of your hypothesis, touching the cause of the abnormal
phenomena observed in your parlour, and would act accordingly.
Now, in this suppositious case, I have taken phenomena of a very common
kind, in order that you might see what are the different steps in an
ordinary process of reasoning, if you will only take the trouble to analyse
it carefully. All the operations I have described, you will see, are
involved in the mind of any man of sense in leading him to a conclusion as
to the course he should take in order to make good a robbery and punish the
offender. I say that you are led, in that case, to your conclusion by
exactly the same train of reasoning as that which a man of science pursues
when he is endeavouring to discover the origin and laws of the most occult
phenomena. The process is, and always must be, the same; and precisely the
same mode of reasoning was employed by Newton and Laplace in their
endeavours to discover and define the causes of the movements of the
heavenly bodies, as you, with your own common sense, would employ to detect
a burglar. The only difference is, that the nature of the inquiry being
more abstruse, every step has to be most carefully watched, so that there
may not be a single crack or flaw in your hypothesis. A flaw or crack in
many of the hypotheses of daily life may be of little or no moment as
affecting the general correctness of the conclusions at which we may
arrive; but, in a scientific inquiry, a fallacy, great or small, is always
of importance, and is sure to be in the long run constantly productive of
mischievous, if not fatal results.
Do not allow yourselves to be misled by the common notion that an
hypothesis is untrustworthy simply because it is an hypothesis. It is often
urged, in respect to some scientific conclusion, that, after all, it is
only an hypothesis. But what more have we to guide us in nine-tenths of the
most important affairs of daily life than hypotheses, and often very
ill-based ones? So that in science, where the evidence of an hypothesis is
subjected to the most rigid examination, we may rightly pursue the same
course. You may have hypotheses and hypotheses. A man may say, if he likes,
that the moon is made of green cheese: that is an hypothesis. But another
man, who has devoted a great deal of time and attention to the subject, and
availed himself of the most powerful telescopes and the results of the
observations of others, declares that in his opinion it is probably
composed of materials very similar to those of which our own earth is made
up: and that is also only an hypothesis. But I need not tell you that there
is an enormous difference in the value of the two hypotheses. That one
which is based on sound scientific knowledge is sure to have a
corresponding value; and that which is a mere hasty random guess is likely
to have but little value. Every great step in our progress in discovering
causes has been made in exactly the same way as that which I have detailed
to you. A person observing the occurrence of certain facts and phenomena
asks, naturally enough, what process, what kind of operation known to occur
in Nature applied to the particular case, will unravel and explain the
mystery? Hence you have the scientific hypothesis; and its value will be
proportionate to the care and completeness with which its basis had been
tested and verified. It is in these matters as in the commonest affairs of
practical life: the guess of the fool will be folly, while the guess of the
wise man will contain wisdom. In all cases, you see that the value of the
result depends on the patience and faithfulness with which the investigator
applies to his hypothesis every possible kind of verification.
I dare say I may have to return to this point by and by; but having dealt
thus far with our logical methods, I must now turn to something which,
perhaps, you may consider more interesting, or, at any rate, more tangible.
But in reality there are but few things that can be more important for you
to understand than the mental processes and the means by which we obtain
scientific conclusions and theories. [Footnote: Those who wish to study
fully the doctrines of which I have endeavoured to give some
rough-and-ready illustrations, must read Mr. John Stuart Mill's _System
of Logic_.] Having granted that the inquiry is a proper one, and having
determined on the nature of the methods we are to pursue and which only can
lead to success, I must now turn to the consideration of our knowledge of
the nature of the processes which have resulted in the present condition of
organic nature.
Here, let me say at once, lest some of you misunderstand me, that I have
extremely little to report. The question of how the present condition of
organic nature came about, resolves itself into two questions. The first
is: How has organic or living matter commenced its existence? And the
second is: How has it been perpetuated? On the second question I shall have
more to say hereafter. But on the first one, what I now have to say will be
for the most part of a negative character.
If you consider what kind of evidence we can have upon this matter, it will
resolve itself into two kinds. We may have historical evidence and we may
have experimental evidence. It is, for example, conceivable, that inasmuch
as the hardened mud which forms a considerable portion of the thickness of
the earth's crust contains faithful records of the past forms of life, and
inasmuch as these differ more and more as we go further down,--it is
possible and conceivable that we might come to some particular bed or
stratum which should contain the remains of those creatures with which
organic life began upon the earth. And if we did so, and if such forms of
organic life were preservable, we should have what I would call historical
evidence of the mode in which organic life began upon this planet. Many
persons will tell you, and indeed you will find it stated in many works on
geology, that this has been done, and that we really possess such a record;
there are some who imagine that the earliest forms of life of which we have
as yet discovered any record, are in truth the forms in which animal life
began upon the globe. The grounds on which they base that supposition are
these:--That if you go through the enormous thickness of the earth's crust
and get down to the older rocks, the higher vertebrate animals--the
quadrupeds, birds, and fishes--cease to be found; beneath them you find
only the invertebrate animals; and in the deepest and lowest rocks those
remains become scantier and scantier, not in any very gradual progression,
however, until, at length, in what are supposed to be the oldest rocks, the
animal remains which are found are almost always confined to four
forms--_Oldhamia_, whose precise nature is not known, whether plant or
animal; _Lingula_, a kind of mollusc; _Trilobites_, a crustacean
animal, having the same essential plan of construction, though differing in
many details from a lobster or crab; and _Hymenocaris_, which is also
a crustacean. So that you have all the _Fauna_ reduced, at this
period, to four forms: one a kind of animal or plant that we know nothing
about, and three undoubted animals--two crustaceans and one mollusc.
I think, considering the organisation of these mollusca and crustacea, and
looking at their very complex nature, that it does indeed require a very
strong imagination to conceive that these were the first created of all
living things. And you must take into consideration the fact that we have
not the slightest proof that these which we call the oldest beds are really
so: I repeat, we have not the slightest proof of it. When you find in some
places that in an enormous thickness of rocks there are but very scanty
traces of life, or absolutely none at all; and that in other parts of the
world rocks of the very same formation are crowded with the records of
living forms, I think it is impossible to place any reliance on the
supposition, or to feel one's self justified in supposing that these are
the forms in which life first commenced. I have not time here to enter upon
the technical grounds upon which I am led to this conclusion,--that could
hardly be done properly in half a dozen lectures on that part alone:--I
must content myself with saying that I do not at all believe that these are
the oldest forms of life.
I turn to the experimental side to see what evidence we have there. To
enable us to say that we know anything about the experimental origination
of organisation and life, the investigator ought to be able to take
inorganic matters, such as carbonic acid, ammonia, water, and salines, in
any sort of inorganic combination, and be able to build them up into
protein matter, and then that protein matter ought to begin to live in an
organic form. That, nobody has done as yet, and I suspect it will be a long
while before anybody does do it. But the thing is by no means so impossible
as it looks; for the researches of modern chemistry have shown us--I won't
say the road towards it, but, if I may so say, they have shown the
finger-post pointing to the road that may lead to it.
It is not many years ago--and you must recollect that Organic Chemistry is
a young science, not above a couple of generations old, you must not expect
too much of it,--it is not many years ago since it was said to be perfectly
impossible to fabricate any organic compound; that is to say, any
non-mineral compound which is to be found in an organised being. It
remained so for a very long period; but it is now a considerable number of
years since a distinguished foreign chemist contrived to fabricate urea, a
substance of a very complex character, which forms one of the waste
products of animal structures. And of late years a number of other
compounds, such as butyric acid, and others, have been added to the list. I
need not tell you that chemistry is an enormous distance from the goal I
indicate; all I wish to point out to you is, that it is by no means safe to
say that that goal may not be reached one day. It may be that it is
impossible for us to produce the conditions requisite to the origination of
life; but we must speak modestly about the matter, and recollect that
Science has put her foot upon the bottom round of the ladder. Truly he
would be a bold man who would venture to predict where she will be fifty
years hence.
There is another inquiry which bears indirectly upon this question, and
upon which I must say a few words. You are all of you aware of the
phenomena of what is called spontaneous generation. Our forefathers, down
to the seventeenth century, or thereabouts, all imagined, in perfectly good
faith, that certain vegetable and animal forms gave birth, in the process
of their decomposition, to insect life. Thus, if you put a piece of meat in
the sun, and allowed it to putrefy, they conceived that the grubs which
soon began to appear were the result of the action of a power of
spontaneous generation which the meat contained. And they could give you
receipts for making various animal and vegetable preparations which would
produce particular kinds of animals. A very distinguished Italian
naturalist, named Redi, took up the question, at a time when everybody
believed in it; among others our own great Harvey, the discoverer of the
circulation of the blood. You will constantly find his name quoted,
however, as an opponent of the doctrine of spontaneous generation; but the
fact is, and you will see it if you will take the trouble to look into his
works, Harvey believed it as profoundly as any man of his time; but he
happened to enunciate a very curious proposition--that every living thing
came from an _egg_; he did not mean to use the word in the sense in
which we now employ it, he only meant to say that every living thing
originated in a little rounded particle of organised substance; and it is
from this circumstance, probably, that the notion of Harvey having opposed
the doctrine originated. Then came Redi, and he proceeded to upset the
doctrine in a very simple manner. He merely covered the piece of meat with
some very fine gauze, and then he exposed it to the same conditions. The
result of this was that no grubs or insects were produced; he proved that
the grubs originated from the insects who came and deposited their eggs in
the meat, and that they were hatched by the heat of the sun. By this kind
of inquiry he thoroughly upset the doctrine of spontaneous generation, for
his time at least.
Then came the discovery and application of the microscope to scientific
inquiries, which showed to naturalists that besides the organisms which
they already knew as living beings and plants, there were an immense number
of minute things which could be obtained apparently almost at will from
decaying vegetable and animal forms. Thus, if you took some ordinary black
pepper or some hay, and steeped it in water, you would find in the course
of a few days that the water had become impregnated with an immense number
of animalcules swimming about in all directions. From facts of this kind
naturalists were led to revive the theory of spontaneous generation. They
were headed here by an English naturalist,--Needham,--and afterwards in
France by the learned Buffon. They said that these things were absolutely
begotten in the water of the decaying substances out of which the infusion
was made. It did not matter whether you took animal or vegetable matter,
you had only to steep it in water and expose it, and you would soon have
plenty of animalcules. They made an hypothesis about this which was a very
fair one. They said, this matter of the animal world, or of the higher
plants, appears to be dead, but in reality it has a sort of dim life about
it, which, if it is placed under fair conditions, will cause it to break up
into the forms of these little animalcules, and they will go through their
lives in the same way as the animal or plant of which they once formed a
part.
The question now became very hotly debated. Spallanzani, an Italian
naturalist, took up opposite views to those of Needham and Buffon, and by
means of certain experiments he showed that it was quite possible to stop
the process by boiling the water, and closing the vessel in which it was
contained. "Oh!" said his opponents; "but what do you know you may be doing
when you heat the air over the water in this way? You may be destroying
some property of the air requisite for the spontaneous generation of the
animalcules."
However, Spallanzani's views were supposed to be upon the right side, and
those of the others fell into discredit; although the fact was that
Spallanzani had not made good his views. Well, then, the subject continued
to be revived from time to time, and experiments were made by several
persons; but these experiments were not altogether satisfactory. It was
found that if you put an infusion in which animalcules would appear if it
were exposed to the air into a vessel and boiled it, and then sealed up the
mouth of the vessel, so that no air, save such as had been heated to 212°,
could reach its contents, that then no animalcules would be found; but if
you took the same vessel and exposed the infusion to the air, then you
would get animalcules. Furthermore, it was found that if you connected the
mouth of the vessel with a red-hot tube in such a way that the air would
have to pass through the tube before reaching the infusion, that then you
would get no animalcules. Yet another thing was noticed: if you took two
flasks containing the same kind of infusion, and left one entirely exposed
to the air, and in the mouth of the other placed a ball of cotton wool, so
that the air would have to filter itself through it before reaching the
infusion, that then, although you might have plenty of animalcules in the
first flask, you would certainly obtain none from the second.
These experiments, you see, all tended towards one conclusion--that the
infusoria were developed from little minute spores or eggs which were
constantly floating in the atmosphere, and which lose their power of
germination if subjected to heat. But one observer now made another
experiment, which seemed to go entirely the other way, and puzzled him
altogether. He took some of this boiled infusion that I have been speaking
of, and by the use of a mercurial bath--a kind of trough used in
laboratories--he deftly inverted a vessel containing the infusion into the
mercury, so that the latter reached a little beyond the level of the mouth
of the _inverted_ vessel. You see that he thus had a quantity of the
infusion shut off from any possible communication with the outer air by
being inverted upon a bed of mercury.
He then prepared some pure oxygen and nitrogen gases, and passed them by
means of a tube going from the outside of the vessel, up through the
mercury into the infusion; so that he thus had it exposed to a perfectly
pure atmosphere of the same constituents as the external air. Of course, he
expected he would get no infusorial animalcules at all in that infusion;
but, to his great dismay and discomfiture, he found he almost always did
get them.
Furthermore, it has been found that experiments made in the manner
described above answer well with most infusions; but that if you fill the
vessel with boiled milk, and then stop the neck with cotton-wool, you
_will_ have infusoria. So that you see there were two experiments that
brought you to one kind of conclusion, and three to another; which was a
most unsatisfactory state of things to arrive at in a scientific inquiry.
Some few years after this, the question began to be very hotly discussed in
France. There was M. Pouchet, a professor at Rouen, a very learned man, but
certainly not a very rigid experimentalist. He published a number of
experiments of his own, some of which were very ingenious, to show that if
you went to work in a proper way, there was a truth in the doctrine of
spontaneous generation. Well, it was one of the most fortunate things in
the world that M. Pouchet took up this question, because it induced a
distinguished French chemist, M. Pasteur, to take up the question on the
other side; and he has certainly worked it out in the most perfect manner.
I am glad to say, too, that he has published his researches in time to
enable me to give you an account of them. He verified all the experiments
which I have just mentioned to you--and then finding those extraordinary
anomalies, as in the case of the mercury bath and the milk, he set himself
to work to discover their nature. In the case of milk he found it to be a
question of temperature. Milk in a fresh state is slightly alkaline; and it
is a very curious circumstance, but this very slight degree of alkalinity
seems to have the effect of preserving the organisms which fall into it
from the air from being destroyed at a temperature of 212°, which is the
boiling point. But if you raise the temperature 10° when you boil it, the
milk behaves like everything else; and if the air with which it comes in
contact, after being boiled at this temperature, is passed through a
red-hot tube, you will not get a trace of organisms.
He then turned his attention to the mercury bath, and found on examination
that the surface of the mercury was almost always covered with a very fine
dust. He found that even the mercury itself was positively full of organic
matters; that from being constantly exposed to the air, it had collected an
immense number of these infusorial organisms from the air. Well, under
these circumstances he felt that the case was quite clear, and that the
mercury was not what it had appeared to M. Schwann to be,--a bar to the
admission of these organisms; but that, in reality, it acted as a reservoir
from which the infusion was immediately supplied with the large quantity
that had so puzzled him.
But not content with explaining the experiments of others, M. Pasteur went
to work to satisfy himself completely. He said to himself: "If my view is
right, and if, in point of fact, all these appearances of spontaneous
generation are altogether due to the falling of minute germs suspended in
the atmosphere,--why, I ought not only to be able to show the germs, but I
ought to be able to catch and sow them, and produce the resulting
organisms." He, accordingly, constructed a very ingenious apparatus to
enable him to accomplish the trapping of the "_germ dust_" in the air.
He fixed in the window of his room a glass tube, in the centre of which he
had placed a ball of gun-cotton, which, as you all know, is ordinary
cotton-wool, which, from having been steeped in strong acid, is converted
into a substance of great explosive power. It is also soluble in alcohol
and ether. One end of the glass tube was, of course, open to the external
air; and at the other end of it he placed an aspirator, a contrivance for
causing a current of the external air to pass through the tube. He kept
this apparatus going for four-and-twenty hours, and then removed the
_dusted_ gun-cotton, and dissolved it in alcohol and ether. He then
allowed this to stand for a few hours, and the result was, that a very fine
dust was gradually deposited at the bottom of it. That dust, on being
transferred to the stage of a microscope, was found to contain an enormous
number of starch grains. You know that the materials of our food and the
greater portion of plants are composed of starch, and we are constantly
making use of it in a variety of ways, so that there is always a quantity
of it suspended in the air. It is these starch grains which form many of
those bright specks that we see dancing in a ray of light sometimes. But
besides these, M. Pasteur found also an immense number of other organic
substances such as spores of fungi, which had been floating about in the
air and had got caged in this way.
He went farther, and said to himself, "If these really are the things that
give rise to the appearance of spontaneous generation, I ought to be able
to take a ball of this dusted gun-cotton and put it into one of my vessels,
containing that boiled infusion which has been kept away from the air, and
in which no infusoria are at present developed, and then, if I am right,
the introduction of this gun-cotton will give rise to organisms."
Accordingly, he took one of these vessels of infusion, which had been kept
eighteen months, without the least appearance of life in it, and by a most
ingenious contrivance, he managed to break it open and introduce such a
ball of gun-cotton, without allowing the infusion or the cotton ball to
come into contact with any air but that which had been subjected to a red
heat, and in twenty-four hours he had the satisfaction of finding all the
indications of what had been hitherto called spontaneous generation. He had
succeeded in catching the germs and developing organisms in the way ho had
anticipated.
It now struck him that the truth of his conclusions might be demonstrated
without all the apparatus he had employed. To do this, he took some
decaying animal or vegetable substance, such as urine, which is an
extremely decomposable substance, or the juice of yeast, or perhaps some
other artificial preparation, and filled a vessel having a long tubular
neck with it. He then boiled the liquid and bent that long neck into an S
shape or zig-zag, leaving it open at the end. The infusion then gave no
trace of any appearance of spontaneous generation, however long it might be
left, as all the germs in the air were deposited in the beginning of the
bent neck. He then cut the tube close to the vessel, and allowed the
ordinary air to have free and direct access; and the result of that was the
appearance of organisms in it, as soon as the infusion had been allowed to
stand long enough to allow of the growth of those it received from the air,
which was about forty-eight hours. The result of M. Pasteur's experiments
proved, therefore, in the most conclusive manner, that all the appearances
of spontaneous generation arose from nothing more than the deposition of
the germs of organisms which were constantly floating in the air.
To this conclusion, however, the objection was made, that if that were the
cause, then the air would contain such an enormous number of these germs,
that it would be a continual fog. But M. Pasteur replied that they are not
there in anything like the number we might suppose, and that an exaggerated
view has been held on that subject; he showed that the chances of animal or
vegetable life appearing in infusions, depend entirely on the conditions
under which they are exposed. If they are exposed to the ordinary
atmosphere around us, why, of course, you may have organisms appearing
early. But, on the other hand, if they are exposed to air at a great
height, or in some very quiet cellar, you will often not find a single
trace of life.
So that M. Pasteur arrived at last at the clear and definite result, that
all these appearances are like the case of the worms in the piece of meat,
which was refuted by Redi, simply germs carried by the air and deposited in
the liquids in which they afterwards appear. For my own part, I conceive
that, with the particulars of M. Pasteur's experiments before us, we cannot
fail to arrive at his conclusions; and that the doctrine of spontaneous
generation has received a final _coup de grâce_.
You, of course, understand that all this in no way interferes with the
_possibility_ of the fabrication of organic matters by the direct
method to which I have referred, remote as that possibility may be.
IV. THE PERPETUATION OF LIVING BEINGS, HEREDITARY TRANSMISSION AND
VARIATION
The inquiry which we undertook, at our last meeting, into the state of our
knowledge of the causes of the phenomena of organic nature,--of the past
and of the present,--resolved itself into two subsidiary inquiries: the
first was, whether we know anything, either historically or experimentally,
of the mode of origin of living beings; the second subsidiary inquiry was,
whether, granting the origin, we know anything about the perpetuation and
modifications of the forms of organic beings. The reply which I had to give
to the first question was altogether negative, and the chief result of my
last lecture was, that, neither historically nor experimentally, do we at
present know anything whatsoever about the origin of living forms. We saw
that, historically, we are not likely to know anything about it, although
we may perhaps learn something experimentally; but that at present we are
an enormous distance from the goal I indicated.
I now, then, take up the next question, What do we know of the
reproduction, the perpetuation, and the modifications of the forms of
living beings, supposing that we have put the question as to their
origination on one side, and have assumed that at present the causes of
their origination are beyond us, and that we know nothing about them? Upon
this question the state of our knowledge is extremely different; it is
exceedingly large: and, if not complete, our experience is certainly most
extensive. It would be impossible to lay it all before you, and the most I
can do, or need do to-night, is to take up the principal points and put
them before you with such prominence as may subserve the purposes of our
present argument.
The method of the perpetuation of organic beings is of two kinds,--the
non-sexual and the sexual. In the first the perpetuation takes place from
and by a particular act of an individual organism, which sometimes may not
be classed as belonging to any sex at all. In the second case, it is in
consequence of the mutual action and interaction of certain portions of the
organisms of usually two distinct individuals,--the male and the female.
The cases of non-sexual perpetuation are by no means so common as the cases
of sexual perpetuation; and they are by no means so common in the animal as
in the vegetable world. You are all probably familiar with the fact, as a
matter of experience, that you can propagate plants by means of what are
called "cuttings"; for example, that by taking a cutting from a geranium
plant, and rearing it properly, by supplying it with light and warmth and
nourishment from the earth, it grows up and takes the form of its parent,
having all the properties and peculiarities of the original plant.
Sometimes this process, which the gardener performs artificially, takes
place naturally; that is to say, a little bulb, or portion of the plant,
detaches itself, drops off, and becomes capable of growing as a separate
thing. That is the case with many bulbous plants, which throw off in this
way secondary bulbs, which are lodged in the ground and become developed
into plants. This is a non-sexual process, and from it results the
repetition or reproduction of the form of the original being from which the
bulb proceeds.
Among animals the same thing takes place. Among the lower forms of animal
life, the infusorial animalculæ we have already spoken of throw off certain
portions, or break themselves up in various directions, sometimes
transversely or sometimes longitudinally; or they may give off buds, which
detach themselves and develop into their proper forms. There is the common
fresh-water polype, for instance, which multiplies itself in this way. Just
in the same way as the gardener is able to multiply and reproduce the
peculiarities and characters of particular plants by means of cuttings, so
can the physiological experimentalist--as was shown by the Abbé Trembley
many years ago--so can he do the same thing with many of the lower forms of
animal life. M. de Trembley showed that you could take a polype and cut it
into two, or four, or many pieces, mutilating it in all directions, and the
pieces would still grow up and reproduce completely the original form of
the animal. These are all cases of non-sexual multiplication, and there are
other instances, and still more extraordinary ones, in which this process
takes place naturally, in a more hidden, a more recondite kind of way. You
are all of you familiar with that little green insect, the _Aphis_ or
blight, as it is called. These little animals, during a very considerable
part of their existence, multiply themselves by means of a kind of internal
budding, the buds being developed into essentially non-sexual animals,
which are neither male nor female; they become converted into young
_Aphides_, which repeat the process, and their offspring after them,
and so on again; you may go on for nine or ten, or even twenty or more
successions; and there is no very good reason to say how soon it might
terminate, or how long it might not go on if the proper conditions of
warmth and nourishment were kept up.
Sexual reproduction is quite a distinct matter. Here, in all these cases,
what is required is the detachment of two portions of the parental
organisms, which portions we know as the egg or the spermatozoon. In plants
it is the ovule and the pollen-grain, as in the flowering plants, or the
ovule and the antherozooid, as in the flowerless. Among all forms of animal
life, the spermatozoa proceed from the male sex, and the egg is the product
of the female. Now, what is remarkable about this mode of reproduction is
this, that the egg by itself, or the spermatozoa by themselves, are unable
to assume the parental form; but if they be brought into contact with one
another, the effect of the mixture of organic substances proceeding from
two sources appears to confer an altogether new vigour to the mixed
product. This process is brought about, as we all know, by the sexual
intercourse of the two sexes, and is called the act of impregnation. The
result of this act on the part of the male and female is, that the
formation of a new being is set up in the ovule or egg; this ovule or egg
soon begins to be divided and subdivided, and to be fashioned into various
complex organs, and eventually to develop into the form of one of its
parents, as I explained in the first lecture. These are the processes by
which the perpetuation of organic beings is secured. Why there should be
the two modes--why this re-invigoration should be required on the part of
the female element we do not know; but it is most assuredly the fact, and
it is presumable, that, however long the process of non-sexual
multiplication could be continued--I say there is good reason to believe
that it would come to an end if a new commencement were not obtained by a
conjunction of the two sexual elements.
That character which is common to these two distinct processes is this,
that, whether we consider the reproduction, or perpetuation, or
modification of organic beings as they take place non-sexually, or as they
may take place sexually--in either case, I say, the offspring has a
constant tendency to assume, speaking generally, the character of the
parent. As I said just now, if you take a slip of a plant, and tend it with
care, it will eventually grow up and develop into a plant like that from
which it had sprung; and this tendency is so strong that, as gardeners
know, this mode of multiplying by means of cuttings is the only secure mode
of propagating very many varieties of plants; the peculiarity of the
primitive stock seems to be better preserved if you propagate it by means
of a slip than if you resort to the sexual mode.
Again, in experiments upon the lower animals, such as the polype, to which
I have referred, it is most extraordinary that, although cut up into
various pieces, each particular piece will grow up into the form of the
primitive stock; the head, if separated, will reproduce the body and the
tail; and if you cut off the tail, you will find that that will reproduce
the body and all the rest of the members, without in any way deviating from
the plan of the organism from which these portions have been detached. And
so far does this go, that some experimentalists have carefully examined the
lower orders of animals,--among them the Abbé Spallanzani, who made a
number of experiments upon snails and salamanders,--and have found that
they might mutilate them to an incredible extent; that you might cut off
the jaw or the greater part of the head, or the leg or the tail, and repeat
the experiment several times, perhaps cutting off the same member again and
again; and yet each of those types would be reproduced according to the
primitive type: Nature making no mistake, never putting on a fresh kind of
leg, or head, or tail, but always tending to repeat and to return to the
primitive type.
It is the same in sexual reproduction: it is a matter of perfectly common
experience, that the tendency on the part of the offspring always is,
speaking broadly, to reproduce the form of the parents. The proverb has it
that the thistle does not bring forth grapes; so, among ourselves, there is
always a likeness, more or less marked and distinct, between children and
their parents. That is a matter of familiar and ordinary observation. We
notice the same thing occurring in the cases of the domestic animals--dogs,
for instance, and their offspring. In all these cases of propagation and
perpetuation, there seems to be a tendency in the offspring to take the
characters of the parental organisms. To that tendency a special name is
given--and as I may very often use it, I will write it up here on this
black-board that you may remember it--it is called _Atavism_; it
expresses this tendency to revert to the ancestral type, and comes from the
Latin word _atavus_, ancestor.
Well, this _Atavism_ which I shall speak of, is, as I said before, one
of the most marked and striking tendencies of organic beings; but, side by
side with this hereditary tendency there is an equally distinct and
remarkable tendency to variation. The tendency to reproduce the original
stock has, as it were, its limits, and side by side with it there is a
tendency to vary in certain directions, as if there were two opposing
powers working upon the organic being, one tending to take it in a straight
line, and the other tending to make it diverge from that straight line,
first to one side and then to the other.
So that you see these two tendencies need not precisely contradict one
another, as the ultimate result may not always be very remote from what
would have been the case if the line had been quite straight.
This tendency to variation is less marked in that mode of propagation which
takes place non-sexually; it is in that mode that the minor characters of
animal and vegetable structures are most completely preserved. Still, it
will happen sometimes, that the gardener, when he has planted a cutting of
some favourite plant, will find, contrary to his expectation, that the slip
grows up a little different from the primitive stock--that it produces
flowers of a different colour or make, or some deviation in one way or
another. This is what is called the "sporting" of plants.
In animals the phenomena of non-sexual propagation are so obscure, that at
present we cannot be said to know much about them; but if we turn to that
mode of perpetuation which results from the sexual process, then we find
variation a perfectly constant occurrence, to a certain extent; and,
indeed, I think that a certain amount of variation from the primitive stock
is the necessary result of the method of sexual propagation itself; for,
inasmuch as the thing propagated proceeds from two organisms of different
sexes and different makes and temperaments, and as the offspring is to be
either of one sex or the other, it is quite clear that it cannot be an
exact diagonal of the two, or it would be of no sex at all; it cannot be an
exact intermediate form between that of each of its parents--it must
deviate to one side or the other. You do not find that the male follows the
precise type of the male parent, nor does the female always inherit the
precise characteristics of the mother,--there is always a proportion of the
female character in the male offspring, and of the male character in the
female offspring. That must be quite plain to all of you who have looked at
all attentively on your own children or those of your neighbours; you will
have noticed how very often it may happen that the son shall exhibit the
maternal type of character, or the daughter possess the characteristics of
the father's family. There are all sorts of intermixtures and intermediate
conditions between the two, where complexion, or beauty, or fifty other
different peculiarities belonging to either side of the house, are
reproduced in other members of the same family. Indeed, it is sometimes to
be remarked in this kind of variation, that the variety belongs, strictly
speaking, to neither of the immediate parents; you will see a child in a
family who is not like either its father or its mother; but some old person
who knew its grandfather or grandmother, or, it may be, an uncle, or,
perhaps, even a more distant relative will see a great similarity between
the child and one of these. In this way it constantly happens that the
characteristic of some previous member of the family comes out and is
reproduced and recognised in the most unexpected manner.
But apart from that matter of general experience, there are some cases
which put that curious mixture in a very clear light. You are aware that
the offspring of the ass and the horse, or rather of the he-ass and the
mare, is what is called a mule; and, on the other hand, the offspring of
the stallion and the she-ass is what is called a hinny. It is a very rare
thing in this country to see a hinny. I never saw one myself; but they have
been very carefully studied. Now, the curious thing is this, that although
you have the same elements in the experiment in each case, the offspring is
entirely different in character, according as the male influence comes from
the ass or the horse. Where the ass is the male, as in the case of the
mule, you find that the head is like that of the ass, that the ears are
long, the tail is tufted at the end, the feet are small, and the voice is
an unmistakable bray; these are all points of similarity to the ass; but,
on the other hand, the barrel of the body and the cut of the neck are much
more like those of the mare. Then, if you look at the hinny,--the result of
the union of the stallion and the she-ass, then you find it is the horse
that has the predominance; that the head is more like that of the horse,
the ears are shorter, the legs coarser, and the type is altogether altered;
while the voice, instead of being a bray, is the ordinary neigh of the
horse. Here, you see, is a most curious thing: you take exactly the same
elements, ass and horse, but you combine the sexes in a different manner,
and the result is modified accordingly. You have in this case, however, a
result which is not general and universal--there is usually an important
preponderance, but not always on the same side.
Here, then, is one intelligible, and, perhaps, necessary cause of
variation: the fact, that there are two sexes sharing in the production of
the offspring, and that the share taken by each is different and variable,
not only for each combination, but also for different members of the same
family.
Secondly, there is a variation, to a certain extent--though, in all
probability, the influence of this cause has been very much
exaggerated--but there is no doubt that variation is produced, to a certain
extent, by what are commonly known as external conditions,--such as
temperature, food, warmth, and moisture. In the long run, every variation
depends, in some sense, upon external conditions, seeing that everything
has a cause of its own. I use the term "external conditions" now in the
sense in which it is ordinarily employed: certain it is, that external
conditions have a definite effect. You may take a plant which has single
flowers, and by dealing with the soil, and nourishment, and so on, you may
by and by convert single flowers into double flowers, and make thorns shoot
out into branches. You may thicken or make various modifications in the
shape of the fruit. In animals, too, you may produce analogous changes in
this way, as in the case of that deep bronze colour which persons rarely
lose after having passed any length of time in tropical countries. You may
also alter the development of the muscles very much, by dint of training;
all the world knows that exercise has a great effect in this way; we always
expect to find the arm of a blacksmith hard and wiry, and possessing a
large development of the brachial muscles. No doubt training, which is one
of the forms of external conditions, converts what are originally only
instructions, teachings, into habits, or, in other words, into
organisations, to a great extent; but this second cause of variation cannot
be considered to be by any means a large one. The third cause that I have
to mention, however, is a very extensive one. It is one that, for want of a
better name, has been called "spontaneous variation"; which means that when
we do not know anything about the cause of phenomena, we call it
spontaneous. In the orderly chain of causes and effects in this world,
there are very few things of which it can be said with truth that they are
spontaneous. Certainly not in these physical matters--in these there is
nothing of the kind--everything depends on previous conditions. But when we
cannot trace the cause of phenomena, we call them spontaneous.
Of these variations, multitudinous as they are, but little is known with
perfect accuracy. I will mention to you some two or three cases, because
they are very remarkable in themselves, and also because I shall want to
use them afterwards. Réaumur, a famous French naturalist, a great many
years ago, in an essay which he wrote upon the art of hatching
chickens--which was indeed a very curious essay--had occasion to speak of
variations and monstrosities. One very remarkable case had come under his
notice of a variation in the form of a human member, in the person of a
Maltese, of the name of Gratio Kelleia, who was born with six fingers upon
each hand, and the like number of toes to each of his feet. That was a case
of spontaneous variation. Nobody knows why he was born with that number of
fingers and toes, and as we don't know, we call it a case of "spontaneous"
variation. There is another remarkable case also. I select these, because
they happen to have been observed and noted very carefully at the time. It
frequently happens that a variation occurs, but the persons who notice it
do not take any care in noting down the particulars, until at length, when
inquiries come to be made, the exact circumstances are forgotten; and
hence, multitudinous as may be such "spontaneous" variations, it is
exceedingly difficult to get at the origin of them.
The second case is one of which you may find the whole details in the
"Philosophical Transactions" for the year 1813, in a paper communicated by
Colonel Humphrey to the President of the Royal Society--"On a new Variety
in the Breed of Sheep," giving an account of a very remarkable breed of
sheep, which at one time was well known in the northern states of America,
and which went by the name of the Ancon or the Otter breed of sheep. In the
year 1791, there was a farmer of the name of Seth Wright in Massachusetts,
who had a flock of sheep, consisting of a ram and, I think, of some twelve
or thirteen ewes. Of this flock of ewes, one at the breeding-time bore a
lamb which was very singularly formed; it had a very long body, very short
legs, and those legs were bowed. I will tell you by and by how this
singular variation in the breed of sheep came to be noted, and to have the
prominence that it now has. For the present, I mention only these two
cases; but the extent of variation in the breed of animals is perfectly
obvious to any one who has studied natural history with ordinary attention,
or to any person who compares animals with others of the same kind. It is
strictly true that there are never any two specimens which are exactly
alike; however similar, they will always differ in some certain particular.
Now let us go back to Atavism--to the hereditary tendency I spoke of. What
will come of a variation when you breed from it, when Atavism comes, if I
may say so, to intersect variation? The two cases of which I have mentioned
the history give a most excellent illustration of what occurs. Gratio
Kelleia, the Maltese, married when he was twenty-two years of age, and, as
I suppose there were no six-fingered ladies in Malta, he married an
ordinary five-fingered person. The result of that marriage was four
children; the first, who was christened Salvator, had six fingers and six
toes, like his father; the second was George, who had five fingers and
toes, but one of them was deformed, showing a tendency to variation; the
third was Andrè; he had five fingers and five toes, quite perfect; the
fourth was a girl, Marie; she had five fingers and five toes, but her
thumbs were deformed, showing a tendency toward the sixth.
These children grew up, and when they came to adult years, they all
married, and of course it happened that they all married five-fingered and
five-toed persons. Now let us see what were the results. Salvator had four
children; they were two boys, a girl, and another boy; the first two boys
and the girl were six-fingered and six-toed like their grandfather; the
fourth boy had only five fingers and five toes. George had only four
children; there were two girls with six fingers and six toes; there was one
girl with six fingers and five toes on the right side, and five fingers and
five toes on the left side, so that she was half and half. The last, a boy,
had five fingers and five toes. The third, Andrè, you will recollect, was
perfectly well-formed, and he had many children whose hands and feet were
all regularly developed. Marie, the last, who, of course, married a man who
had only five fingers, had four children; the first, a boy, was born with
six toes, but the other three were normal.
Now observe what very extraordinary phenomena are presented here. You have
an accidental variation giving rise to what you may call a monstrosity; you
have that monstrosity or variation diluted in the first instance by an
admixture with a female of normal construction, and you would naturally
expect that, in the results of such an union, the monstrosity, if repeated,
would be in equal proportion with the normal type; that is to say, that the
children would be half and half, some taking the peculiarity of the father,
and the others being of the purely normal type of the mother; but you see
we have a great preponderance of the abnormal type. Well, this comes to be
mixed once more with the pure, the normal type, and the abnormal is again
produced in large proportion, notwithstanding the second dilution. Now what
would have happened if these abnormal types had intermarried with each
other; that is to say, suppose the two boys of Salvator had taken it into
their heads to marry their first cousins, the two first girls of George,
their uncle? You will remember that these are all of the abnormal type of
their grandfather. The result would probably have been, that their
offspring would have been in every case a further development of that
abnormal type. You see it is only in the fourth, in the person of Marie,
that the tendency, when it appears but slightly in the second generation,
is washed out in the third, while the progeny of Andrè, who escaped in the
first instance, escape altogether.
We have in this case a good example of nature's tendency to the
perpetuation of a variation. Here it is certainly a variation which earned
with it no use or benefit; and yet you see the tendency to perpetuation may
be so strong, that, notwithstanding a great admixture of pure blood, the
variety continues itself up to the third generation, which is largely
marked with it. In this case, as I have said, there was no means of the
second generation intermarrying with any but five-fingered persons, and the
question naturally suggests itself, What would have been the result of such
marriage? Réaumur narrates this case only as far as the third generation.
Certainly it would have been an exceedingly curious thing if we could have
traced this matter any further; had the cousins intermarried, a
six-fingered variety of the human race might have been set up.
To show you that this supposition is by no means an unreasonable one, let
me now point out what took place in the case of Seth Wright's sheep, where
it happened to be a matter of moment to him to obtain a breed or raise a
flock of sheep like that accidental variety that I have described--and I
will tell you why. In that part of Massachusetts where Seth Wright was
living, the fields were separated by fences, and the sheep, which were very
active and robust, would roam abroad, and without much difficulty jump over
these fences into other people's farms. As a matter of course, this
exuberant activity on the part of the sheep constantly gave rise to all
sorts of quarrels, bickerings, and contentions among the farmers of the
neighbourhood; so it occurred to Seth Wright, who was, like his successors,
more or less 'cute, that if he could get a stock of sheep like those with
the bandy legs, they would not be able to jump over the fences so readily;
and he acted upon that idea. He killed his old ram, and as soon as the
young one arrived at maturity, he bred altogether from it. The result was
even more striking than in the human experiment which I mentioned just now.
Colonel Humphreys testifies that it always happened that the offspring were
either pure Ancons or pure ordinary sheep; that in no case was there any
mixing of the Ancons with the others. In consequence of this, in the course
of a very few years, the farmer was able to get a very considerable flock
of this variety, and a large number of them were spread throughout
Massachusetts. Most unfortunately, however--I suppose it was because they
were so common--nobody took enough notice of them to preserve their
skeletons; and although Colonel Humphreys states that he sent a skeleton to
the President of the Royal Society at the same time that he forwarded his
paper, I am afraid that the variety has entirely disappeared; for a short
time after these sheep had become prevalent in that district, the Merino
sheep were introduced; and as their wool was much more valuable, and as
they were a quiet race of sheep, and showed no tendency to trespasser jump
over fences, the Otter breed of sheep, the wool of which was inferior to
that of the Merino, was gradually allowed to die out.
You see that these facts illustrate perfectly well what may be done if you
take care to breed from stocks that are similar to each other. After having
got a variation, if, by crossing a variation with the original stock, you
multiply that variation, and then take care to keep that variation distinct
from the original stock, and make them breed together,--then you may almost
certainly produce a race whose tendency to continue the variation is
exceedingly strong.
This is what is called "selection"; and it is by exactly the same process
as that by which Seth Wright bred his Ancon sheep, that our breeds of
cattle, dogs, and fowls are obtained. There are some possibilities of
exception, but still, speaking broadly, I may say that this is the way in
which all our varied races of domestic animals have arisen; and you must
understand that it is not one peculiarity or one characteristic alone in
which animals may vary. There is not a single peculiarity or characteristic
of any kind, bodily or mental, in which offspring may not vary to a certain
extent from the parent and other animals.
Among ourselves this is well known. The simplest physical peculiarity is
mostly reproduced. I know a case of a woman who has the lobe of one of her
ears a little flattened. An ordinary observer might scarcely notice it, and
yet every one of her children has an approximation to the same peculiarity
to some extent. If you look at the other extreme, too, the gravest
diseases, such as gout, scrofula, and consumption, may be handed down with
just the same certainty and persistence as we noticed in the perpetuation
of the bandy legs of the Ancon sheep.
However, these facts are best illustrated in animals, and the extent of the
variation, as is well known, is very remarkable in dogs. For example, there
are some dogs very much smaller than others; indeed, the variation is so
enormous that probably the smallest dog would be about the size of the head
of the largest; there are very great variations in the structural forms not
only of the skeleton but also in the shape of the skull, and in the
proportions of the face and the disposition of the teeth.
The Pointer, the Retriever, Bulldog, and the Terrier differ very greatly,
and yet there is every reason to believe that every one of these races has
arisen from the same source,--that all the most important races have arisen
by this selective breeding from accidental variation.
A still more striking case of what may be done by selective breeding, and
it is a better case, because there is no chance of that partial infusion of
error to which I alluded, has been studied very carefully by Mr.
Darwin,--the case of the domestic pigeons. I dare say there may be some
among you who may be pigeon _fanciers_, and I wish you to understand
that in approaching the subject, I would speak with all humility and
hesitation, as I regret to say that I am not a pigeon fancier. I know it is
a great art and mystery, and a thing upon which a man must not speak
lightly; but I shall endeavour, as far as my understanding goes, to give
you a summary of the published and unpublished information which I have
gained from Mr. Darwin.
Among the enormous variety,--I believe there are somewhere about a hundred
and fifty kinds of pigeons,--there are four kinds which may be selected as
representing the extremest divergences of one kind from another. Their
names are the Carrier, the Pouter, the Fantail, and the Tumbler. In these
large diagrams that I have here they are each represented in their relative
sizes to each other. This first one is the Carrier; you will notice this
large excrescence on its beak; it has a comparatively small head; there is
a bare space round the eyes; it has a long neck, a very long beak, very
strong legs, large feet, long wings, and so on. The second one is the
Pouter, a very large bird, with very long legs and beak. It is called the
Pouter because it is in the habit of causing its gullet to swell up by
inflating it with air. I should tell you that all pigeons have a tendency
to do this at times, but in the Pouter it is carried to an enormous extent.
The birds appear to be quite proud of their power of swelling and puffing
themselves out in this way; and I think it is about as droll a sight as you
can well see to look at a cage full of these pigeons puffing and blowing
themselves out in this ridiculous manner.
This diagram is a representation of the third kind I mentioned--the
Fantail. It is, you see, a small bird, with exceedingly small legs and a
very small beak. It is most curiously distinguished by the size and extent
of its tail, which, instead of containing twelve feathers, may have many
more,--say thirty, or even more--I believe there are some with as many as
forty-two. This bird has a curious habit of spreading out the feathers of
its tail in such a way that they reach forward and touch its head; and if
this can be accomplished, I believe it is looked upon as a point of great
beauty.
But here is the last great variety,--the Tumbler; and of that great
variety, one of the principal kinds, and one most prized, is the specimen
represented here--the short-faced Tumbler. Its beak, you see, is reduced to
a mere nothing. Just compare the beak of this one and that of the first
one, the Carrier--I believe the orthodox comparison of the head and beak of
a thoroughly well-bred Tumbler is to stick an oat into a cherry, and that
will give you the proper relative proportions of the beak and head. The
feet and legs are exceedingly small, and the bird appears to be quite a
dwarf when placed side by side with this great Carrier.
These are differences enough in regard to their external appearance; but
these differences are by no means the whole or even the most important of
the differences which obtain between these birds. There is hardly a single
point of their structure which has not become more or less altered; and to
give you an idea of how extensive these alterations are, I have here some
very good skeletons, for which I am indebted to my friend, Mr. Tegetmeier,
a great authority in these matters; by means of which, if you examine them
by and by, you will be able to see the enormous difference in their bony
structures.
I had the privilege, some time ago, of access to some important MSS. of Mr.
Darwin, who, I may tell you, has taken very great pains and spent much
valuable time and attention on the investigation of these variations, and
getting together all the facts that bear upon them. I obtained from these
MSS. the following summary of the differences between the domestic breeds
of pigeons; that is to say, a notification of the various points in which
their organisation differs. In the first place, the back of the skull may
differ a good deal, and the development of the bones of the face may vary a
great deal; the back varies a good deal; the shape of the lower jaw varies;
the tongue varies very greatly, not only in correlation to the length and
size of the beak, but it seems also to have a kind of independent variation
of its own. Then the amount of naked skin round the eyes, and at the base
of the beak, may vary enormously; so may the length of the eyelids, the
shape of the nostrils, and the length of the neck. I have already noticed
the habit of blowing out the gullet, so remarkable in the Pouter, and
comparatively so in the others. There are great differences, too, in the
size of the female and the male, the shape of the body, the number and
width of the processes of the ribs, the development of the ribs, and the
size, shape, and development of the breastbone. We may notice, too--and I
mention the fact because it has been disputed by what is assumed to be high
authority,--the variation in the number of the sacral vertebrae. The number
of these varies from eleven to fourteen, and that without any diminution in
the number of the vertebrae of the back or of the tail. Then the number and
position of the tail-feathers may vary enormously, and so may the number of
the primary and secondary feathers of the wings. Again, the length of the
feet and of the beak,--although they have no relation to each other, yet
appear to go together,--that is, you have a long beak wherever you have
long feet. There are differences also in the periods of the acquirement of
the perfect plumage--the size and shape of the eggs--the nature of flight,
and the powers of flight--so-called _"homing"_ birds having enormous
flying powers; [Footnote: The _"Carrier,"_ I learn from Mr.
Tegetmeier, does not _carry_; a high-bred bird of this breed being but
a poor flier. The birds which fly long distances, and come home--"homing"
birds-and are consequently used as carriers, are not "carriers" in the
fancy sense.] while, on the other hand, the little Tumbler is so called
because of its extraordinary faculty of turning head over heels in the air,
instead of pursuing a direct course. And, lastly, the dispositions and
voices of the birds may vary. Thus the case of the pigeons shows you that
there is hardly a single particular--whether of instinct, or habit, or bony
structure, or of plumage--of either the internal economy or the external
shape, in which some variation or change may not take place, which, by
selective breeding, may become perpetuated, and form the foundation of, and
give rise to, a new race.
If you carry in your mind's eye these four varieties of pigeons, you will
bear with you as good a notion as you can have, perhaps, of the enormous
extent to which a deviation from a primitive type may be carried by means
of this process of selective breeding.
V. THE CONDITIONS OF EXISTENCE AS AFFECTING THE PERPETUATION OF LIVING
BEINGS
In the last Lecture I endeavoured to prove to you that, while, as a general
rule, organic beings tend to reproduce their kind, there is in them, also,
a constantly recurring tendency to vary--to vary to a greater or to a less
extent. Such a variety, I pointed out to you, might arise from causes which
we do not understand; we therefore called it spontaneous; and it might come
into existence as a definite and marked thing, without any gradations
between itself and the form which preceded it. I further pointed out, that
such a variety having once arisen, might be perpetuated to some extent, and
indeed to a very marked extent, without any direct interference, or without
any exercise of that process which we called selection. And then I stated
further, that by such selection, when exercised artificially--if you took
care to breed only from those forms which presented the same peculiarities
of any variety which had arisen in this manner--the variation might be
perpetuated, as far as we can see, indefinitely.
The next question, and it is an important one for us, is this: Is there any
limit to the amount of variation from the primitive stock which can be
produced by this process of selective breeding? In considering this
question, it will be useful to class the characteristics, in respect of
which organic beings vary, under two heads: we may consider structural
characteristics, and we may consider physiological characteristics.
In the first place, as regards structural characteristics, I endeavoured to
show you, by the skeletons which I had upon the table, and by reference to
a great many well-ascertained facts, that the different breeds of Pigeons,
the Carriers, Pouters, and Tumblers, might vary in any of their internal
and important structural characters to a very great degree; not only might
there be changes in the proportions of the skull, and the characters of the
feet and beaks, and so on; but that there might be an absolute difference
in the number of the vertebrae of the back, as in the sacral vertebras of
the Pouter; and so great is the extent of the variation in these and
similar characters that I pointed out to you, by reference to the skeletons
and the diagrams, that these extreme varieties may absolutely differ more
from one another in their structural characters than do what naturalists
call distinct SPECIES of pigeons; that is to say, that they differ so much
in structure that there is a greater difference between the Pouter and the
Tumbler than there is between such wild and distinct forms as the Rock
Pigeon or the Ring Pigeon, or the Ring Pigeon and the Stock Dove; and
indeed the differences are of greater value than this, for the structural
differences between these domesticated pigeons are such as would be
admitted by a naturalist, supposing he knew nothing at all about their
origin, to entitle them to constitute even distinct genera.
As I have used this term SPECIES, and shall probably use it a good deal, I
had better perhaps devote a word or two to explaining what I mean by it.
Animals and plants are divided into groups, which become gradually smaller,
beginning with a KINGDOM, which is divided into SUB-KINGDOMS; then come the
smaller divisions called PROVINCES; and so on from a PROVINCE to a CLASS,
from a CLASS to an ORDER, from ORDERS to FAMILIES, and from these to
GENERA, until we come at length to the smallest groups of animals which can
be defined one from the other by constant characters, which are not sexual;
and these are what naturalists call SPECIES in practice, whatever they may
do in theory.
If, in a state of nature, you find any two groups of living beings, which
are separated one from the other by some constantly-recurring
characteristic, I don't care how slight and trivial, so long as it is
defined and constant, and does not depend on sexual peculiarities, then all
naturalists agree in calling them two species; that is what is meant by the
use of the word species--that is to say, it is, for the practical
naturalist, a mere question of structural differences. [Footnote: I lay
stress here on the _practical_ signification of "Species." Whether a
physiological test between species exist or not, it is hardly ever
applicable by the practical naturalist.] We have seen now--to repeat this
point once more, and it is very essential that we should rightly understand
it--we have seen that breeds, known to have been derived from a common
stock by selection, may be as different in their structure from the
original stock as species may be distinct from each other.
But is the like true of the physiological characteristics of animals? Do
the physiological differences of varieties amount in degree to those
observed between forms which naturalists call distinct species? This is a
most important point for us to consider.
As regards the great majority of physiological characteristics, there is no
doubt that they are capable of being developed, increased, and modified by
selection.
There is no doubt that breeds may be made as different as species in many
physiological characters. I have already pointed out to you very briefly
the different habits of the breeds of Pigeons, all of which depend upon
their physiological peculiarities--as the peculiar habit of tumbling, in
the Tumbler--the peculiarities of flight, in the "homing" birds--the
strange habit of spreading out the tail, and walking in a peculiar fashion,
in the Fantail--and, lastly, the habit of blowing out the gullet, so
characteristic of the Pouter. These are all due to physiological
modifications, and in all these respects these birds differ as much from
each other as any two ordinary species do.
So with Dogs in their habits and instincts. It is a physiological
peculiarity which leads the Greyhound to chase its prey by sight--that
enables the Beagle to track it by the scent--that impels the Terrier to its
rat-hunting propensity--and that leads the Retriever to its habit of
retrieving. These habits and instincts are all the results of physiological
differences and peculiarities, which have been developed from a common
stock, at least there is every reason to believe so. But it is a most
singular circumstance, that while you may run through almost the whole
series of physiological processes, without finding a check to your
argument, you come at last to a point where you do find a check, and that
is in the reproductive processes. For there is a most singular circumstance
in respect to natural species--at least about some of them--and it would be
sufficient for the purposes of this argument if it were true of only one of
them, but there is, in fact, a great number of such cases--and that is,
that, similar as they may appear to be to mere races or breeds, they
present a marked peculiarity in the reproductive process. If you breed from
the male and female of the same race, you of course have offspring of the
like kind, and if you make the offspring breed together, you obtain the
same result, and if you breed from these again, you will still have the
same kind of offspring; there is no check. But if you take members of two
distinct species, however similar they may be to each other, and make them
breed together, you will find a check, with some modifications and
exceptions, however, which I shall speak of presently. If you cross two
such species with each other, then--although you may get offspring in the
case of the first cross, yet, if you attempt to breed from the products of
that crossing, which are what are called HYBRIDS--that is, if you couple a
male and a female hybrid--then the result is that in ninety-nine cases out
of a hundred you will get no offspring at all; there will be no result
whatsoever.
The reason of this is quite obvious in some cases; the male hybrids,
although possessing all the external appearances and characteristics of
perfect animals, are physiologically imperfect and deficient in the
structural parts of the reproductive elements necessary to generation. It
is said to be invariably the case with the male mule, the cross between the
Ass and the Mare; and hence it is, that, although crossing the Horse with
the Ass is easy enough, and is constantly done, as far as I am aware, if
you take two mules, a male and a female, and endeavour to breed from them,
you get no offspring whatever; no generation will take place. This is what
is called the sterility of the hybrids between two distinct species.
You see that this is a very extraordinary circumstance; one does not see
why it should be. The common teleological explanation is, that it is to
prevent the impurity of the blood resulting from the crossing of one
species with another, but you see it does not in reality do anything of the
kind. There is nothing in this fact that hybrids cannot breed with each
other, to establish such a theory; there is nothing to prevent the Horse
breeding with the Ass, or the Ass with the Horse. So that this explanation
breaks down, as a great many explanations of this kind do, that are only
founded on mere assumptions.
Thus you see that there is a great difference between "mongrels," which are
crosses between distinct races, and "hybrids," which are crosses between
distinct species. The mongrels are, so far as we know, fertile with one
another. But between species, in many cases, you cannot succeed in
obtaining even the first cross; at any rate it is quite certain that the
hybrids are often absolutely infertile one with another.
Here is a feature, then, great or small as it may be, which distinguishes
natural species of animals. Can we find any approximation to this in the
different races known to be produced by selective breeding from a common
stock? Up to the present time the answer to that question is absolutely a
negative one. As far as we know at present, there is nothing approximating
to this check. In crossing the breeds between the Fantail and the Pouter,
the Carrier and the Tumbler, or any other variety or race you may name--so
far as we know at present--there is no difficulty in breeding together the
mongrels. Take the Carrier and the Fantail, for instance, and let them
represent the Horse and the Ass in the case of distinct species; then you
have, as the result of their breeding, the Carrier-Fantail mongrel,--we
will say the male and female mongrel,--and, as far as we know, these two
when crossed would not be less fertile than the original cross, or than
Carrier with Carrier. Here, you see, is a physiological contrast between
the races produced by selective modification and natural species. I shall
inquire into the value of this fact, and of some modifying circumstances by
and by; for the present I merely put it broadly before you.
But while considering this question of the limitations of species, a word
must be said about what is called RECURRENCE--the tendency of races which
have been developed by selective breeding from varieties to return to their
primitive type. This is supposed by many to put an absolute limit to the
extent of selective and all other variations. People say, "It is all very
well to talk about producing these different races, but you know very well
that if you turned all these birds wild, these Pouters, and Carriers, and
so on, they would all return to their primitive stock." This is very
commonly assumed to be a fact, and it is an argument that is commonly
brought forward as conclusive; but if you will take the trouble to inquire
into it rather closely, I think you will find that it is not worth very
much. The first question of course is, Do they thus return to the primitive
stock? And commonly as the thing is assumed and accepted, it is extremely
difficult to get anything like good evidence of it. It is constantly said,
for example, that if domesticated Horses are turned wild, as they have been
in some parts of Asia Minor and South America, that they return at once to
the primitive stock from which they were bred. But the first answer that
you make to this assumption is, to ask who knows what the primitive stock
was; and the second answer is, that in that case the wild Horses of Asia
Minor ought to be exactly like the wild Horses of South America. If they
are both like the same thing, they ought manifestly to be like each other!
The best authorities, however, tell you that it is quite different. The
wild Horse of Asia is said to be of a dun colour, with a largish head, and
a great many other peculiarities; while the best authorities on the wild
Horses of South America tell you that there is no similarity between their
wild Horses and those of Asia Minor; the cut of their heads is very
different, and they are commonly chestnut or bay-coloured. It is quite
clear, therefore, that as by these facts there ought to have been two
primitive stocks, they go for nothing in support of the assumption that
races recur to one primitive stock, and so far as this evidence is
concerned, it falls to the ground.
Suppose for a moment that it were so, and that domesticated races, when
turned wild, did return to some common condition, I cannot see that this
would prove much more than that similar conditions are likely to produce
similar results; and that when you take back domesticated animals into what
we call natural conditions, you do exactly the same thing as if you
carefully undid all the work you had gone through, for the purpose of
bringing the animal from its wild to its domesticated state. I do not see
anything very wonderful in the fact, if it took all that trouble to get it
from a wild state, that it should go back into its original state as soon
as you removed the conditions which produced the variation to the
domesticated form. There is an important fact, however, forcibly brought
forward by Mr. Darwin, which has been noticed in connection with the
breeding of domesticated pigeons; and it is, that however different these
breeds of pigeons may be from each other, and we have already noticed the
great differences in these breeds, that if, among any of those variations,
you chance to have a blue pigeon turn up, it will be sure to have the black
bars across the wings, which are characteristic of the original wild stock,
the Rock Pigeon.
Now, this is certainly a very remarkable circumstance; but I do not see
myself how it tells very strongly either one way or the other. I think, in
fact, that this argument in favour of recurrence to the primitive type
might prove a great deal too much for those who so constantly bring it
forward. For example, Mr. Darwin has very forcibly urged, that nothing is
commoner than if you examine a dun horse--and I had an opportunity of
verifying this illustration lately while in the islands of the West
Highlands, where there are a great many dun horses--to find that horse
exhibit a long black stripe down his back, very often stripes on his
shoulder, and very often stripes on his legs. I, myself, saw a pony of this
description a short time ago, in a baker's cart, near Rothesay, in Bute: it
had the long stripe down the back, and stripes on the shoulders and legs,
just like those of the Ass, the Quagga, and the Zebra. Now, if we interpret
the theory of recurrence as applied to this case, might it not be said that
here was a case of a variation exhibiting the characters and conditions of
an animal occupying something like an intermediate position between the
Horse, the Ass, the Quagga, and the Zebra, and from which these had been
developed? In the same way with regard even to Man. Every anatomist will
tell you that there is nothing commoner, in dissecting the human body, than
to meet with what are called muscular variations--that is, if you dissect
two bodies very carefully, you will probably find that the modes of
attachment and insertion of the muscles are not exactly the same in both,
there being great peculiarities in the mode in which the muscles are
arranged; and it is very singular, that in some dissections of the human
body you will come upon arrangements of the muscles very similar indeed to
the same parts in the Apes. Is the conclusion in that case to be, that this
is like the black bars in the case of the Pigeon, and that it indicates a
recurrence to the primitive type from which the animals have been probably
developed? Truly, I think that the opponents of modification and variation
had better leave the argument of recurrence alone, or it may prove
altogether too strong for them.
To sum up,--the evidence as far as we have gone is against the argument as
to any limit to divergences, so far as structure is concerned; and in
favour of a physiological limitation. By selective breeding we can produce
structural divergences as great as those of species, but we cannot produce
equal physiological divergences. For the present I leave the question
there.
Now, the next problem that lies before us--and it is an extremely important
one--is this: Does this selective breeding occur in nature? Because, if
there is no proof of it, all that I have been telling you goes for nothing
in accounting for the origin of species. Are natural causes competent to
play the part of selection in perpetuating varieties? Here we labour under
very great difficulties. In the last lecture I had occasion to point out to
you the extreme difficulty of obtaining evidence even of the first origin
of those varieties which we know to have occurred in domesticated animals.
I told you, that almost always the origin of these varieties is overlooked,
so that I could only produce two or three cases, as that of Gratio Kelleia
and of the Ancon sheep. People forget, or do not take notice of them until
they come to have a prominence; and if that is true of artificial cases,
under our own eyes, and in animals in our own care, how much more difficult
it must be to have at first hand good evidence of the origin of varieties
in nature! Indeed, I do not know that it is possible by direct evidence to
prove the origin of a variety in nature, or to prove selective breeding;
but I will tell you what we can prove--and this comes to the same
thing--that varieties exist in nature within the limits of species, and,
what is more, that when a variety has come into existence in nature, there
are natural causes and conditions, which are amply competent to play the
part of a selective breeder; and although that is not quite the evidence
that one would like to have--though it is not direct testimony--yet it is
exceeding good and exceedingly powerful evidence in its way.
As to the first point, of varieties existing among natural species, I might
appeal to the universal experience of every naturalist, and of any person
who has ever turned any attention at all to the characteristics of plants
and animals in a state of nature; but I may as well take a few definite
cases, and I will begin with Man himself.
I am one of those who believe that, at present, there is no evidence
whatever for saying, that mankind sprang originally from any more than a
single pair; I must say, that I cannot see any good ground whatever, or
even any tenable sort of evidence, for believing that there is more than
one species of Man. Nevertheless, as you know, just as there are numbers of
varieties in animals, so there are remarkable varieties of men. I speak not
merely of those broad and distinct variations which you see at a glance.
Everybody, of course, knows the difference between a Negro and a white man,
and can tell a Chinaman from an Englishman. They each have peculiar
characteristics of colour and physiognomy; but you must recollect that the
characters of these races go very far deeper--they extend to the bony
structure, and to the characters of that most important of all organs to
us--the brain; so that, among men belonging to different races, or even
within the same race, one man shall have a brain a third, or half, or even
seventy per cent, bigger than another; and if you take the whole range of
human brains, you will find a variation in some cases of a hundred per
cent. Apart from these variations in the size of the brain, the characters
of the skull vary. Thus if I draw the figures of a Mongol and of a Negro
head on the blackboard, in the case of the last the breadth would be about
seven-tenths, and in the other it would be nine-tenths of the total length.
So that you see there is abundant evidence of variation among men in their
natural condition. And if you turn to other animals there is just the same
thing. The fox, for example, which has a very large geographical
distribution all over Europe, and parts of Asia, and on the American
Continent, varies greatly. There are mostly large foxes in the North, and
smaller ones in the South. In Germany alone the foresters reckon some eight
different sorts.
Of the tiger, no one supposes that there is more than one species; they
extend from the hottest parts of Bengal, into the dry, cold, bitter steppes
of Siberia, into a latitude of 50°,--so that they may even prey upon the
reindeer. These tigers have exceedingly different characteristics, but
still they all keep their general features, so that there is no doubt as to
their being tigers. The Siberian tiger has a thick fur, a small mane, and a
longitudinal stripe down the back, while the tigers of Java and Sumatra
differ in many important respects from the tigers of Northern Asia. So
lions vary; so birds vary; and so, if you go further back and lower down in
creation, you find that fishes vary. In different streams, in the same
country even, you will find the trout to be quite different to each other
and easily recognisable by those who fish in the particular streams. There
is the same differences in leeches; leech collectors can easily point out
to you the differences and the peculiarities which you yourself would
probably pass by; so with fresh-water mussels; so, in fact, with every
animal you can mention.
In plants there is the same kind of variation. Take such a case even as the
common bramble. The botanists are all at war about it; some of them wanting
to make out that there are many species of it, and others maintaining that
they are but many varieties of one species; and they cannot settle to this
day which is a species and which is a variety!
So that there can be no doubt whatsoever that any plant and any animal may
vary in nature; that varieties may arise in the way I have described--as
spontaneous varieties--and that those varieties may be perpetuated in the
same way that I have shown you spontaneous varieties are perpetuated; I
say, therefore, that there can be no doubt as to the origin and
perpetuation of varieties in nature.
But the question now is:--Does selection take place in nature? Is there
anything like the operation of man in exercising selective breeding, taking
place in nature? You will observe that, at present, I say nothing about
species; I wish to confine myself to the consideration of the production of
those natural races which everybody admits to exist. The question is,
whether in nature there are causes competent to produce races, just in the
same way as man is able to produce by selection, such races of animals as
we have already noticed.
When a variety has arisen, the CONDITIONS OF EXISTENCE are such as to
exercise an influence which is exactly comparable to that of artificial
selection. By Conditions of Existence I mean two things--there are
conditions which are furnished by the physical, the inorganic world, and
there are conditions of existence which are furnished by the organic world.
There is, in the first place, CLIMATE; under that head I include only
temperature and the varied amount of moisture of particular places. In the
next place there is what is technically called STATION, which means--given
the climate, the particular kind of place in which an animal or a plant
lives or grows; for example, the station of a fish is in the water, of a
fresh-water fish in fresh water; the station of a marine fish is in the
sea, and a marine animal may have a station higher or deeper. So again with
land animals: the differences in their stations are those of different
soils and neighbourhoods; some being best adapted to a calcareous, and
others to an arenaceous soil. The third condition of existence is FOOD, by
which I mean food in the broadest sense, the supply of the materials
necessary to the existence of an organic being; in the case of a plant the
inorganic matters, such as carbonic acid, water, ammonia, and the earthy
salts or salines; in the case of the animal the inorganic and organic
matters, which we have seen they require; then these are all, at least the
first two, what we may call the inorganic or physical conditions of
existence. Food takes a mid-place, and then come the organic conditions; by
which I mean the conditions which depend upon the state of the rest of the
organic creation, upon the number and kind of living beings, with which an
animal is surrounded. You may class these under two heads: there are
organic beings, which operate as _opponents_, and there are organic
beings which operate as _helpers_ to any given organic creature. The
opponents may be of two kinds: there are the _indirect opponents_,
which are what we may call _rivals_; and there are the _direct
opponents_, those which strive to destroy the creature; and these we
call _enemies_. By rivals I mean, of course, in the case of plants,
those which require for their support the same kind of soil and station,
and, among animals, those which require the same kind of station, or food,
or climate; those are the indirect opponents; the direct opponents are, of
course, those which prey upon an animal or vegetable. The _helpers_
may also be regarded as direct and indirect: in the case of a carnivorous
animal, for example, a particular herbaceous plant may, in multiplying, be
an indirect helper, by enabling the herbivora on which the carnivore preys
to get more food, and thus to nourish the carnivore more abundantly; the
direct helper may be best illustrated by reference to some parasitic
creature, such as the tape-worm. The tape-worm exists in the human
intestines, so that the fewer there are of men the fewer there will be of
tape-worms, other things being alike. It is a humiliating reflection,
perhaps, that we may be classed as direct helpers to the tape-worm, but the
fact is so: we can all see that if there were no men there would be no
tape-worms.
It is extremely difficult to estimate, in a proper way, the importance and
the working of the Conditions of Existence. I do not think there were any
of us who had the remotest notion of properly estimating them until the
publication of Mr. Darwin's work, which has placed them before us with
remarkable clearness; and I must endeavour, as far as I can in my own
fashion, to give you some notion of how they work. We shall find it easiest
to take a simple case, and one as free as possible from every kind of
complication.
I will suppose, therefore, that all the habitable part of this globe--the
dry land, amounting to about 51,000,000 square miles--I will suppose that
the whole of that dry land has the same climate, and that it is composed of
the same kind of rock or soil, so that there will be the same station
everywhere; we thus get rid of the peculiar influence of different climates
and stations. I will then imagine that there shall be but one organic being
in the world, and that shall be a plant. In this we start fair. Its food is
to be carbonic acid, water and ammonia, and the saline matters in the soil,
which are, by the supposition, everywhere alike. We take one single plant,
with no opponents, no helpers, and no rivals; it is to be a "fair field,
and no favour." Now, I will ask you to imagine further that it shall be a
plant which shall produce every year fifty seeds, which is a very moderate
number for a plant to produce; and that, by the action of the winds and
currents, these seeds shall be equally and gradually distributed over the
whole surface of the land. I want you now to trace out what will occur, and
you will observe that I am not talking fallaciously any more than a
mathematician does when he expounds his problem. If you show that the
conditions of your problem are such as may actually occur in Nature and do
not transgress any of the known laws of Nature in working out your
proposition, then you are as safe in the conclusion you arrive at as is the
mathematician in arriving at the solution of his problem. In science, the
only way of getting rid of the complications with which a subject of this
kind is environed, is to work in this deductive method. What will be the
result, then? I will suppose that every plant requires one square foot of
ground to live upon; and the result will be that, in the course of nine
years, the plant will have occupied every single available spot in the
whole globe! I have chalked upon the blackboard the figures by which I
arrive at the result:--
Plants. Plants.
1 x 50 in 1st year = 50
50 x 50 " 2nd " = 2,500
2,500 x 50 " 3rd " = 125,000
125,000 x 50 " 4th " = 6,250,000
6,250,000 x 50 " 5th " = 312,500,000
312,500,000 x 50 " 6th " = 15,625,000,000
15,625,000,000 x 50 " 7th " = 781,250,000,000
781,250,000,000 x 50 " 8th " = 39,062,500,000,000
39,062,500,000,000 x 50 " 9th " = 1,953,125,000,000,000
51,000,000 square miles--the )
dry surface of the earth x )
27,878,400--the number of ) = sq. ft. 1,421,798,400,000,000
sq. ft. in 1 sq. mile ) ---------------------
being 531,326,600,000,000
square feet less than would be required at the end of the ninth
year.
You will see from this that, at the end of the first year the single plant
will have produced fifty more of its kind; by the end of the second year
these will have increased to 2,500; and so on, in succeeding years, you get
beyond even trillions; and I am not at all sure that I could tell you what
the proper arithmetical denomination of the total number really is; but, at
any rate, you will understand the meaning of all those noughts. Then you
see that, at the bottom, I have taken the 51,000,000 of square miles,
constituting the surface of the dry land; and as the number of square feet
are placed under and subtracted from the number of seeds that would be
produced in the ninth year, you can see at once that there would be an
immense number more of plants than there would be square feet of ground for
their accommodation. This is certainly quite enough to prove my point; that
between the eighth and ninth year after being planted the single plant
would have stocked the whole available surface of the earth.
This is a thing which is hardly conceivable--it seems hardly
imaginable--yet it is so. It is indeed simply the law of Malthus
exemplified. Mr. Malthus was a clergyman, who worked out this subject most
minutely and truthfully some years ago; he showed quite clearly--and
although he was much abused for his conclusions at the time, they have
never yet been disproved and never will be--he showed that in consequence
of the increase in the number of organic beings in a geometrical ratio,
while the means of existence cannot be made to increase in the same ratio,
that there must come a time when the number of organic beings will be in
excess of the power of production of nutriment, and that thus some check
must arise to the further increase of those organic beings. At the end of
the ninth year we have seen that each plant would not be able to get its
full square foot of ground, and at the end of another year it would have to
share that space with fifty others the produce of the seeds which it would
give off.
What, then, takes place? Every plant grows up, flourishes, occupies its
square foot of ground, and gives off its fifty seeds; but notice this, that
out of this number only one can come to anything; there is thus, as it
were, forty-nine chances to one against its growing up; it depends upon the
most fortuitous circumstances whether any one of these fifty seeds shall
grow up and flourish, or whether it shall die and perish. This is what Mr.
Darwin has drawn attention to, and called the "STRUGGLE FOR EXISTENCE"; and
I have taken this simple case of a plant because some people imagine that
the phrase seems to imply a sort of fight.
I have taken this plant and shown you that this is the result of the ratio
of the increase, the necessary result of the arrival of a time coming for
every species when exactly as many members must be destroyed as are born;
that is the inevitable ultimate result of the rate of production. Now, what
is the result of all this? I have said that there are forty-nine struggling
against every one; and it amounts to this, that the smallest possible start
given to any one seed may give it an advantage which will enable it to get
ahead of all the others; anything that will enable any one of these seeds
to germinate six hours before any of the others will, other things being
alike, enable it to choke them out altogether. I have shown you that there
is no particular in which plants will not vary from each other; it is quite
possible that one of our imaginary plants may vary in such a character as
the thickness of the integument of its seeds; it might happen that one of
the plants might produce seeds having a thinner integument, and that would
enable the seeds of that plant to germinate a little quicker than those of
any of the others, and those seeds would most inevitably extinguish the
forty-nine times as many that were struggling with them.
I have put it in this way, but you see the practical result of the process
is the same as if some person had nurtured the one and destroyed the other
seeds. It does not matter how the variation is produced, so long as it is
once allowed to occur. The variation in the plant once fairly started tends
to become hereditary and reproduce itself; the seeds would spread
themselves in the same way and take part in the struggle with the
forty-nine hundred, or forty-nine thousand, with which they might be
exposed. Thus, by degrees, this variety with some slight organic change or
modification, must spread itself over the whole surface of the habitable
globe, and extirpate or replace the other kinds. That is what is meant by
NATURAL SELECTION; that is the kind of argument by which it is perfectly
demonstrable that the conditions of existence may play exactly the same
part for natural varieties as man does for domesticated varieties. No one
doubts at all that particular circumstances may be more favourable for one
plant and less so for another, and the moment you admit that, you admit the
selective power of nature. Now, although I have been putting a hypothetical
case, you must not suppose that I have been reasoning hypothetically. There
are plenty of direct experiments which bear out what we may call the theory
of natural selection; there is extremely good authority for the statement
that if you take the seed of mixed varieties of wheat and sow it,
collecting the seed next year and sowing it again, at length you will find
that out of all your varieties only two or three have lived, or perhaps
even only one. There were one or two varieties which were best fitted to
get on, and they have killed out the other kinds in just the same way and
with just the same certainty as if you had taken the trouble to remove
them. As I have already said, the operation of nature is exactly the same
as the artificial operation of man.
But if this be true of that simple case, which I put before you, where
there is nothing but the rivalry of one member of a species with others,
what must be the operation of selective conditions, when you recollect as a
matter of fact, that for every species of animal or plant there are fifty
or a hundred species which might all, more or less, be comprehended in the
same climate, food, and station;--that every plant has multitudinous
animals which prey upon it, and which are its direct opponents; and that
these have other animals preying upon them,--that every plant has its
indirect helpers in the birds that scatter abroad its seed, and the animals
that manure it with their dung;--I say, when these things are considered,
it seems impossible that any variation which may arise in a species in
nature should not tend in some way or other either to be a little better or
worse than the previous stock; if it is a little better it will have an
advantage over and tend to extirpate the latter in this crush and struggle;
and if it is a little worse it will itself be extirpated.
I know nothing that more appropriately expresses this, than the phrase,
"the struggle for existence "; because it brings before your minds, in a
vivid sort of way, some of the simplest possible circumstances connected
with it. When a struggle is intense there must be some who are sure to be
trodden down, crushed, and overpowered by others; and there will be some
who just manage to get through only by the help of the slightest accident.
I recollect reading an account of the famous retreat of the French troops,
under Napoleon, from Moscow. Worn out, tired, and dejected, they at length
came to a great river over which there was but one bridge for the passage
of the vast army. Disorganised and demoralised as that army was, the
struggle must certainly have been a terrible one--every one heeding only
himself, and crushing through the ranks and treading down his fellows. The
writer of the narrative, who was himself one of those who were fortunate
enough to succeed in getting over, and not among the thousands who were
left behind or forced into the river, ascribed his escape to the fact that
he saw striding onward through the mass a great strong fellow,--one of the
French Cuirassiers, who had on a large blue cloak-and he had enough
presence of mind to catch and retain a hold of this strong man's cloak. He
says, "I caught hold of his cloak, and although he swore at me and cut at
and struck me by turns, and at last, when he found he could not shake me
off, fell to entreating me to leave go or I should prevent him from
escaping, besides not assisting myself, I still kept tight hold of him, and
would not quit my grasp until he had at last dragged me through." Here you
see was a case of selective saving--if we may so term it--depending for its
success on the strength of the cloth of the Cuirassier's cloak. It is the
same in nature; every species has its bridge of Beresina; it has to fight
its way through and struggle with other species; and when well-nigh
overpowered, it may be that the smallest chance, something in its colour,
perhaps--the minutest circumstance--will turn the scale one way or the
other.
Suppose that by a variation of the black race it had produced the white man
at any time--you know that the Negroes are said to believe this to have
been the case, and to imagine that Cain was the first white man, and that
we are his descendants--suppose that this had ever happened, and that the
first residence of this human being was on the West Coast of Africa. There
is no great structural difference between the white man and the Negro, and
yet there is something so singularly different in the constitution of the
two, that the malarias of that country, which do not hurt the black at all,
cut off and destroy the white. Then you see there would have been a
selective operation performed; if the white man had risen in that way, he
would have been selected out and removed by means of the malaria. Now there
really is a very curious case of selection of this sort among pigs, and it
is a case of selection of colour too. In the woods of Florida there are a
great many pigs, and it is a very curious thing that they are all black,
every one of them. Professor Wyman was there some years ago, and on
noticing no pigs but these black ones, he asked some of the people how it
was that they had no white pigs, and the reply was that in the woods of
Florida there was a root which they called the Paint Root, and that if the
white pigs were to eat any of it, it had the effect of making their hoofs
crack, and they died, but if the black pigs ate any of it, it did not hurt
them at all. Here was a very simple case of natural selection. A skilful
breeder could not more carefully develop the black breed of pigs, and weed
out all the white pigs, than the Paint Root does.
To show you how remarkably indirect may be such natural selective agencies
as I have referred to, I will conclude by noticing a case mentioned by Mr.
Darwin, and which is certainly one of the most curious of its kind. It is
that of the Humble Bee. It has been noticed that there are a great many
more humble bees in the neighbourhood of towns, than out in the open
country; and the explanation of the matter is this: the humble bees build
nests, in which they store their honey and deposit the larvæ and eggs. The
field mice are amazingly fond of the honey and larvæ; therefore, wherever
there are plenty of field mice, as in the country, the humble bees are kept
down; but in the neighbourhood of towns, the number of cats which prowl
about the fields eat up the field mice, and of course the more mice they
eat up the less there are to prey upon the larvæ of the bees--the cats are
therefore the INDIRECT HELPERS of the bees. [Footnote: The humble bees, on
the other hand, are direct helpers of some plants, such as the heartsease
and red clover, which are fertilised by the visits of the bees; and they
are indirect helpers of the numerous insects which are more or less
completely supported by the heartsease and red clover.] Coming back a step
farther we may say that the old maids are also indirect friends of the
humble bees, and indirect enemies of the field mice, as they keep the cats
which eat up the latter! This is an illustration somewhat beneath the
dignity of the subject, perhaps, but it occurs to me in passing, and with
it I will conclude this lecture.
VI. A CRITICAL EXAMINATION OF THE POSITION OF MR. DARWIN'S WORK, "ON THE
ORIGIN OF SPECIES," IN RELATION TO THE COMPLETE THEORY OF THE CAUSES OF THE
PHENOMENA OF ORGANIC NATURE
In the preceding five lectures I have endeavoured to give you an account of
those facts, and of those reasonings from facts, which form the data upon
which all theories regarding the causes of the phenomena of organic nature
must be based. And, although I have had frequent occasion to quote Mr.
Darwin--as all persons hereafter, in speaking upon these subjects, will
have occasion to quote his famous book on the "Origin of Species,"--you
must yet remember that, wherever I have quoted him, it has not been upon
theoretical points, or for statements in any way connected with his
particular speculations, but on matters of fact, brought forward by
himself, or collected by himself, and which appear incidentally in his
book. If a man _will_ make a book, professing to discuss a single
question, an encyclopædia, I cannot help it.
Now, having had an opportunity of considering in this sort of way the
different statements bearing upon all theories whatsoever, I have to lay
before you, as fairly as I can, what is Mr. Darwin's view of the matter and
what position his theories hold, when judged by the principles which I have
previously laid down, as deciding our judgments upon all theories and
hypotheses.
I have already stated to you that the inquiry respecting the causes of the
phenomena of organic nature resolves itself into two problems--the first
being the question of the origination of living or organic beings; and the
second being the totally distinct problem of the modification and
perpetuation of organic beings when they have already come into existence.
The first question Mr. Darwin does not touch; he does not deal with it at
all; but he says:--"Given the origin of organic matter--supposing its
creation to have already taken place, my object is to show in consequence
of what laws and what demonstrable properties of organic matter, and of its
environments, such states of organic nature as those with which we are
acquainted must have come about." This, you will observe, is a perfectly
legitimate proposition; every person has a right to define the limits of
the inquiry which he sets before himself; and yet it is a most singular
thing that in all the multifarious, and, not unfrequently, ignorant attacks
which have been made upon the "Origin of Species," there is nothing which
has been more speciously criticised than this particular limitation. If
people have nothing else to urge against the book, they say--"Well, after
all, you see Mr. Darwin's explanation of the 'Origin of Species' is not
good for much, because, in the long run, he admits that he does not know
how organic matter began to exist. But if you admit any special creation
for the first particle of organic matter you may just as well admit it for
all the rest; five hundred or five thousand distinct creations are just as
intelligible, and just as little difficult to understand, as one." The
answer to these cavils is two-fold. In the first place, all human inquiry
must stop somewhere; all our knowledge and all our investigation cannot
take us beyond the limits set by the finite and restricted character of our
faculties, or destroy the endless unknown, which accompanies, like its
shadow, the endless procession of phenomena. So far as I can venture to
offer an opinion on such a matter, the purpose of our being in existence,
the highest object that human beings can set before themselves, is not the
pursuit of any such chimera as the annihilation of the unknown; but it is
simply the unwearied endeavour to remove its boundaries a little further
from our little sphere of action.
I wonder if any historian would for a moment admit the objection, that it
is preposterous to trouble ourselves about the history of the Roman Empire,
because we do not know anything positive about the origin and first
building of the city of Rome! Would it be a fair objection to urge,
respecting the sublime discoveries of a Newton, or a Kepler, those great
philosophers, whose discoveries have been of the profoundest benefit and
service to all men--to say to them--"After all that you have told us as to
how the planets revolve, and how they are maintained in their orbits, you
cannot tell us what is the cause of the origin of the sun, moon, and stars.
So what is the use of what you have done?" Yet these objections would not
be one whit more preposterous than the objections which have been made to
the "Origin of Species." Mr. Darwin, then, had a perfect right to limit his
inquiry as he pleased, and the only question for us--the inquiry being so
limited--is to ascertain whether the method of his inquiry is sound or
unsound; whether he has obeyed the canons which must guide and govern all
investigation, or whether he has broken them; and it was because our
inquiry this evening is essentially limited to that question, that I spent
a good deal of time in a former lecture (which, perhaps some of you thought
might have been better employed), in endeavouring to illustrate the method
and nature of scientific inquiry in general. We shall now have to put in
practice the principles that I then laid down.
I stated to you in substance, if not in words, that wherever there are
complex masses of phenomena to be inquired into, whether they be phenomena
of the affairs of daily life, or whether they belong to the more abstruse
and difficult problems laid before the philosopher, our course of
proceeding in unravelling that complex chain of phenomena with a view to
get at its cause, is always the same; in all cases we must invent an
hypothesis; we must place before ourselves some more or less likely
supposition respecting that cause; and then, having assumed an hypothesis,
having supposed a cause for the phenomena in question, we must endeavour,
on the one hand, to demonstrate our hypothesis, or, on the other, to upset
and reject it altogether, by testing it in three ways. We must, in the
first place, be prepared to prove that the supposed causes of the phenomena
exist in nature; that they are what the logicians call _vera
causæ_--true causes;--in the next place, we should be prepared to show
that the assumed causes of the phenomena are competent to produce such
phenomena as those which we wish to explain by them; and in the last place,
we ought to be able to show that no other known causes are competent to
produce these phenomena. If we can succeed in satisfying these three
conditions we shall have demonstrated our hypothesis; or rather I ought to
say we shall have proved it as far as certainty is possible for us; for,
after all, there is no one of our surest convictions which may not be
upset, or at any rate modified by a further accession of knowledge. It was
because it satisfied these conditions that we accepted the hypothesis as to
the disappearance of the tea-pot and spoons in the case I supposed in a
previous lecture; we found that our hypothesis on that subject was tenable
and valid, because the supposed cause existed in nature, because it was
competent to account for the phenomena, and because no other known cause
was competent to account for them; and it is upon similar grounds that any
hypothesis you choose to name is accepted in science as tenable and valid.
What is Mr. Darwin's hypothesis? As I apprehend it--for I have put it into
a shape more convenient for common purposes than I could find
_verbatim_ in his book--as I apprehend it, I say, it is, that all the
phenomena of organic nature, past and present, result from, or are caused
by, the inter-action of those properties of organic matter, which we have
called ATAVISM and VARIABILITY, with the CONDITIONS OF EXISTENCE, or, in
other words,--given the existence of organic matter, its tendency to
transmit its properties, and its tendency occasionally to vary; and,
lastly, given the conditions of existence by which organic matter is
surrounded--that these put together are the causes of the Present and of
the Past conditions of ORGANIC NATURE.
Such is the hypothesis as I understand it. Now let us see how it will stand
the various tests which I laid down just now. In the first place, do these
supposed causes of the phenomena exist in nature? Is it the fact that, in
nature, these properties of organic matter--atavism and variability--and
those phenomena which we have called the conditions of existence,--is it
true that they exist? Well, of course, if they do not exist, all that I
have told you in the last three or four lectures must be incorrect, because
I have been attempting to prove that they do exist, and I take it that
there is abundant evidence that they do exist; so far, therefore, the
hypothesis does not break down.
But in the next place comes a much more difficult inquiry:--Are the causes
indicated competent to give rise to the phenomena of organic nature? I
suspect that this is indubitable to a certain extent. It is demonstrable, I
think, as I have endeavoured to show you, that they are perfectly competent
to give rise to all the phenomena which are exhibited by RACES in nature.
Furthermore, I believe that they are quite competent to account for all
that we may call purely structural phenomena which are exhibited by SPECIES
in nature. On that point also I have already enlarged somewhat. Again, I
think that the causes assumed are competent to account for most of the
physiological characteristics of species, and I not only think that they
are competent to account for them, but I think that they account for many
things which otherwise remain wholly unaccountable and inexplicable, and I
may say incomprehensible. For a full exposition of the grounds on which
this conviction is based, I must refer you to Mr. Darwin's work; all that I
can do now is to illustrate what I have said by two or three cases taken
almost at random.
I drew your attention, on a previous evening, to the facts which are
embodied in our systems of Classification, which are the results of the
examination and comparison of the different members of the animal kingdom
one with another. I mentioned that the whole of the animal kingdom is
divisible into five sub-kingdoms; that each of these sub-kingdoms is again
divisible into provinces; that each province may be divided into classes,
and the classes into the successively smaller groups, orders, families,
genera, and species.
Now, in each of these groups the resemblance in structure among the members
of the group is closer in proportion as the group is smaller. Thus, a man
and a worm are members of the animal kingdom in virtue of certain
apparently slight though really fundamental resemblances which they
present. But a man and a fish are members of the same sub-kingdom
_Vertebrata_, because they are much more like one another than either
of them is to a worm, or a snail, or any member of the other sub-kingdoms.
For similar reasons men and horses are arranged as members of the same
Class, _Mammalia_; men and apes as members of the same Order,
_Primates_; and if there were any animals more like men than they were
like any of the apes, and yet different from men in important and constant
particulars of their organisation, we should rank them as members of the
same Family, or of the same Genus, but as of distinct Species.
That it is possible to arrange all the varied forms of animals into groups,
having this sort of singular subordination one to the other, is a very
remarkable circumstance; but, as Mr. Darwin remarks, this is a result which
is quite to be expected, if the principles which he lays down be correct.
Take the case of the races which are known to be produced by the operation
of atavism and variability, and the conditions of existence which check and
modify these tendencies. Take the case of the pigeons that I brought before
you: there it was shown that they might be all classed as belonging to some
one of five principal divisions, and that within these divisions other
subordinate groups might be formed. The members of these groups are related
to one another in just the same way as the genera of a family, and the
groups themselves as the families of an order, or the orders of a class;
while all have the same sort of structural relations with the wild
rock-pigeon, as the members of any great natural group have with a real or
imaginary typical form. Now, we know that all varieties of pigeons of every
kind have arisen by a process of selective breeding from a common stock,
the rock-pigeon; hence, you see, that if all species of animals have
proceeded from some common stock, the general character of their structural
relations, and of our systems of classification, which express those
relations, would be just what we find them to be. In other words, the
hypothetical cause is, so far, competent to produce effects similar to
those of the real cause.
Take, again, another set of very remarkable facts,--the existence of what
are called rudimentary organs, organs for which we can find no obvious use,
in the particular animal economy in which they are found, and yet which are
there.
Such are the splint-like bones in the leg of the horse, which I here show
you, and which correspond with bones which belong to certain toes and
fingers in the human hand and foot. In the horse you see they are quite
rudimentary, and bear neither toes nor fingers; so that the horse has only
one "finger" in his fore-foot and one "toe" in his hind-foot. But it is a
very curious thing that the animals closely allied to the horse show more
toes than he; as the rhinoceros, for instance: he has these extra toes well
formed, and anatomical facts show very clearly that he is very closely
related to the horse indeed. So we may say that animals, in an anatomical
sense nearly related to the horse, have those parts which are rudimentary
in him fully developed.
Again, the sheep and the cow have no cutting-teeth, but only a hard pad in
the upper jaw. That is the common characteristic of ruminants in general.
But the calf has in its upper jaw some rudiments of teeth which never are
developed, and never play the part of teeth at all. Well, if you go back in
time, you find some of the older, now extinct, allies of the ruminants have
well-developed teeth in their upper jaws; and at the present day the pig
(which is in structure closely connected with ruminants) has well-developed
teeth in its upper jaw; so that here is another instance of organs
well-developed and very useful, in one animal, represented by rudimentary
organs, for which we can discover no purpose whatsoever in another closely
allied animal. The whalebone whale, again, has horny "whalebone" plates in
its mouth, and no teeth; but the young foetal whale before it is born has
teeth in its jaws; they, however, are never used, and they never come to
anything. But other members of the group to which the whale belongs have
well-developed teeth in both jaws.
Upon any hypothesis of special creation, facts of this kind appear to me to
be entirely unaccountable and inexplicable, but they cease to be so if you
accept Mr. Darwin's hypothesis, and see reason for believing that the
whalebone whale and the whale with teeth in its mouth both sprang from a
whale that had teeth, and that the teeth of the foetal whale are merely
remnants--recollections, if we may so say--of the extinct whale. So in the
case of the horse and the rhinoceros: suppose that both have descended by
modification from some earlier form which had the normal number of toes,
and the persistence of the rudimentary bones which no longer support toes
in the horse becomes comprehensible.
In the language that we speak in England, and in the language of the
Greeks, there are identical verbal roots, or elements entering into the
composition of words. That fact remains unintelligible so long as we
suppose English and Greek to be independently created tongues; but when it
is shown that both languages are descended from one original, we give an
explanation of that resemblance. In the same way the existence of identical
structural roots, if I may so term them, entering into the composition of
widely different animals, is striking evidence in favour of the descent of
those animals from a common original.
To turn to another kind of illustration:--If you regard the whole series of
stratified rocks--that enormous thickness of sixty or seventy thousand feet
that I have mentioned before, constituting the only record we have of a
most prodigious lapse of time, that time being, in all probability, but a
fraction of that of which we have no record;--if you observe in these
successive strata of rocks successive groups of animals arising and dying
out, a constant succession, giving you the same kind of impression, as you
travel from one group of strata to another, as you would have in travelling
from one country to another;--when you find this constant succession of
forms, their traces obliterated except to the man of science--when you look
at this wonderful history, and ask what it means, it is only a paltering
with words if you are offered the reply--"They were so created."
But if, on the other hand, you look on all forms of organised beings as the
results of the gradual modification of a primitive type, the facts receive
a meaning, and you see that these older conditions are the necessary
predecessors of the present. Viewed in this light the facts of
palaeontology receive a meaning--upon any other hypothesis I am unable to
see, in the slightest degree, what knowledge or signification we are to
draw out of them. Again, note as bearing upon the same point, the singular
likeness which obtains between the successive Faunæ and Floræ, whose
remains are preserved on the rocks: you never find any great and enormous
difference between the immediately successive Faunæ and Floræ, unless you
have reason to believe there has also been a great lapse of time or a great
change of conditions. The animals, for instance, of the newest tertiary
rocks, in any part of the world, are always, and without exception, found
to be closely allied with those which now live in that part of the world.
For example, in Europe, Asia, and Africa, the large mammals are at present
rhinoceroses, hippopotamuses, elephants, lions, tigers, oxen, horses, &c.;
and if you examine the newest tertiary deposits, which contain the animals
and plants which immediately preceded those which now exist in the same
country, you do not find gigantic specimens of ant-eaters and kangaroos,
but you find rhinoceroses, elephants, lions, tigers, &c.,--of different
species to those now living--but still their close allies. If you turn to
South America, where, at the present day, we have great sloths and
armadilloes and creatures of that kind, what do you find in the newest
tertiaries? You find the great sloth-like creature, the _Megatherium_,
and the great armadillo, the _Glyptodon_, and so on. And if you go to
Australia you find the same law holds good, namely, that that condition of
organic nature which has preceded the one which now exists, presents
differences perhaps of species, and of genera, but that the great types of
organic structure are the same as those which now flourish.
What meaning has this fact upon any other hypothesis or supposition than
one of successive modification? But if the population of the world, in any
age, is the result of the gradual modification of the forms which peopled
it in the preceding age--if that has been the case, it is intelligible
enough; because we may expect that the creature that results from the
modification of an elephantine mammal shall be something like an elephant,
and the creature which is produced by the modification of an armadillo-like
mammal shall be like an armadillo. Upon that supposition, I say, the facts
are intelligible; upon any other, that I am aware of, they are not.
So far, the facts of palæontology are consistent with almost any form of
the doctrine of progressive modification; they would not be absolutely
inconsistent with the wild speculations of De Maillet, or with the less
objectionable hypothesis of Lamarck. But Mr. Darwin's views have one
peculiar merit; and that is, that they are perfectly consistent with an
array of facts which are utterly inconsistent with, and fatal to, any other
hypothesis of progressive modification which has yet been advanced. It is
one remarkable peculiarity of Mr. Darwin's hypothesis that it involves no
necessary progression or incessant modification, and that it is perfectly
consistent with the persistence for any length of time of a given primitive
stock, contemporaneously with its modifications. To return to the case of
the domestic breeds of pigeons, for example; you have the dove-cot pigeon,
which closely resembles the rock pigeon, from which they all started,
existing at the same time with the others. And if species are developed in
the same way in nature, a primitive stock and its modifications may,
occasionally, all find the conditions fitted for their existence; and
though they come into competition, to a certain extent, with one another,
the derivative species may not necessarily extirpate the primitive one, or
_vice versa_.
Now palæontology shows us many facts which are perfectly harmonious with
these observed effects of the process by which Mr. Darwin supposes species
to have originated, but which appear to me to be totally inconsistent with
any other hypothesis which has been proposed. There are some groups of
animals and plants, in the fossil world, which have been said to belong to
"persistent types," because they have persisted, with very little change
indeed, through a very great range of time, while everything about them has
changed largely. There are families of fishes whose type of construction
has persisted all the way from the carboniferous strata right up to the
cretaceous; and others which have lasted through almost the whole range of
the secondary rocks, and from the lias to the older tertiaries. It is
something stupendous this--to consider a genus lasting without essential
modifications through all this enormous lapse of time while almost
everything else was changed and modified.
Thus I have no doubt that Mr. Darwin's hypothesis will be found competent
to explain the majority of the phenomena exhibited by species in nature;
but in an earlier lecture I spoke cautiously with respect to its power of
explaining all the physiological peculiarities of species.
There is, in fact, one set of these peculiarities which the theory of
selective modification, as it stands at present, is not wholly competent to
explain, and that is the group of phenomena which I mentioned to you under
the name of Hybridism, and which I explained to consist in the sterility of
the offspring of certain species when crossed one with another. It matters
not one whit whether this sterility is universal, or whether it exists only
in a single case. Every hypothesis is bound to explain, or, at any rate,
not be inconsistent with, the whole of the facts which it professes to
account for; and if there is a single one of these facts which can be shown
to be inconsistent with (I do not merely mean inexplicable by, but contrary
to) the hypothesis, the hypothesis falls to the ground,--it is worth
nothing. One fact with which it is positively inconsistent is worth as
much, and as powerful in negativing the hypothesis, as five hundred. If I
am right in thus defining the obligations of an hypothesis, Mr. Darwin, in
order to place his views beyond the reach of all possible assault, ought to
be able to demonstrate the possibility of developing from a particular
stock by selective breeding, two forms, which should either be unable to
cross one with another, or whose cross-bred offspring should be infertile
with one another.
For, you see, if you have not done that you have not strictly fulfilled all
the conditions of the problem; you have not shown that you can produce, by
the cause assumed, all the phenomena which you have in nature. Here are the
phenomena of Hybridism staring you in the face, and you cannot say, "I can,
by selective modification, produce these same results." Now, it is admitted
on all hands that, at present, so far as experiments have gone, it has not
been found possible to produce this complete physiological divergence by
selective breeding. I stated this very clearly before, and I now refer to
the point, because, if it could be proved, not only that this _has_
not been done, but that it _cannot_ be done; if it could be
demonstrated that it is impossible to breed selectively, from any stock, a
form which shall not breed with another, produced from the same stock; and
if we were shown that this must be the necessary and inevitable results of
all experiments, I hold that Mr. Darwin's hypothesis would be utterly
shattered.
But has this been done? or what is really the state of the case? It is
simply that, so far as we have gone yet with our breeding, we have not
produced from a common stock two breeds which are not more or less fertile
with one another.
I do not know that there is a single fact which would justify any one in
saying that any degree of sterility has been observed between breeds
absolutely known to have been produced by selective breeding from a common
stock. On the other hand, I do not know that there is a single fact which
can justify any one in asserting that such sterility cannot be produced by
proper experimentation. For my own part, I see every reason to believe that
it may, and will be so produced. For, as Mr. Darwin has very properly
urged, when we consider the phenomena of sterility, we find they are most
capricious; we do not know what it is that the sterility depends on. There
are some animals which will not breed in captivity; whether it arises from
the simple fact of their being shut up and deprived of their liberty, or
not, we do not know, but they certainly will not breed. What an astounding
thing this is, to find one of the most important of all functions
annihilated by mere imprisonment!
So, again, there are cases known of animals which have been thought by
naturalists to be undoubted species, which have yielded perfectly fertile
hybrids; while there are other species which present what everybody
believes to be varieties [Footnote: And as I conceive with very good
reason; but if any objector urges that we cannot prove that they have been
produced by artificial or natural selection, the objection must be
admitted--ultra-sceptical as it is. But in science, scepticism is a duty.]
which are more or less infertile with one another. There are other cases
which are truly extraordinary; there is one, for example, which has been
carefully examined,--of two kinds of sea-weed, of which the male element of
the one, which we may call A, fertilises the female element of the other,
B; while the male element of B will not fertilise the female element of A;
so that, while the former experiment seems to show us that they are
_varieties_, the latter leads to the conviction that they are
_species_.
When we see how capricious and uncertain this sterility is, how unknown the
conditions on which it depends, I say that we have no right to affirm that
those conditions will not be better understood by and by, and we have no
ground for supposing that we may not be able to experiment so as to obtain
that crucial result which I mentioned just now. So that though Mr. Darwin's
hypothesis does not completely extricate us from this difficulty at
present, we have not the least right to say it will not do so.
There is a wide gulf between the thing you cannot explain and the thing
that upsets you altogether. There is hardly any hypothesis in this world
which has not some fact in connection with it which has not been explained,
but that is a very different affair to a fact that entirely opposes your
hypothesis; in this case all you can say is, that your hypothesis is in the
same position as a good many others.
Now, as to the third test, that there are no other causes competent to
explain the phenomena, I explained to you that one should be able to say of
an hypothesis, that no other known causes than those supposed by it are
competent to give rise to the phenomena. Here, I think, Mr. Darwin's view
is pretty strong. I really believe that the alternative is either Darwinism
or nothing, for I do not know of any rational conception or theory of the
organic universe which has any scientific position at all beside Mr.
Darwin's. I do not know of any proposition that has been put before us with
the intention of explaining the phenomena of organic nature, which has in
its favour a thousandth part of the evidence which may be adduced in favour
of Mr. Darwin's views. Whatever may be the objections to his views,
certainly all other theories are absolutely out of court.
Take the Lamarckian hypothesis, for example. Lamarck was a great
naturalist, and to a certain extent went the right way to work; he argued
from what was undoubtedly a true cause of some of the phenomena of organic
nature. He said it is a matter of experience that an animal may be modified
more or less in consequence of its desires and consequent actions. Thus, if
a man exercise himself as a blacksmith, his arms will become strong and
muscular; such organic modification is a result of this particular action
and exercise. Lamarck thought that by a very simple supposition based on
this truth he could explain the origin of the various animal species: he
said, for example, that the short-legged birds which live on fish had been
converted into the long-legged waders by desiring to get the fish without
wetting their feathers, and so stretching their legs more and more through
successive generations. If Lamarck could have shown experimentally that
even races of animals could be produced in this way, there might have been
some ground for his speculations. But he could show nothing of the kind,
and his hypothesis has pretty well dropped into oblivion, as it deserved to
do. I said in an earlier lecture that there are hypotheses and hypotheses,
and when people tell you that Mr. Darwin's strongly-based hypothesis is
nothing but a mere modification of Lamarck's, you will know what to think
of their capacity for forming a judgment on this subject.
But you must recollect that when I say I think it is either Mr. Darwin's
hypothesis or nothing; that either we must take his view, or look upon the
whole of organic nature as an enigma, the meaning of which is wholly hidden
from us; you must understand that I mean that I accept it provisionally, in
exactly the same way as I accept any other hypothesis. Men of science do
not pledge themselves to creeds; they are bound by articles of no sort;
there is not a single belief that it is not a bounden duty with them to
hold with a light hand and to part with cheerfully, the moment it is really
proved to be contrary to any fact, great or small. And if, in course of
time I see good reasons for such a proceeding, I shall have no hesitation
in coming before you, and pointing out any change in my opinion without
finding the slightest occasion to blush for so doing. So I say that we
accept this view as we accept any other, so long as it will help us, and we
feel bound to retain it only so long as it will serve our great
purpose--the improvement of Man's estate and the widening of his knowledge.
The moment this, or any other conception, ceases to be useful for these
purposes, away with it to the four winds; we care not what becomes of it!
But to say truth, although it has been my business to attend closely to the
controversies roused by the publication of Mr. Darwin's book, I think that
not one of the enormous mass of objections and obstacles which have been
raised is of any very great value, except that sterility case which I
brought before you just now. All the rest are misunderstandings of some
sort, arising either from prejudice, or want of knowledge, or still more
from want of patience and care in reading the work.
For you must recollect that it is not a book to be read with as much ease
as its pleasant style may lead you to imagine. You spin through it as if it
were a novel the first time you read it, and think you know all about it;
the second time you read it you think you know rather less about it; and
the third time, you are amazed to find how little you have really
apprehended its vast scope and objects. I can positively say that I never
take it up without finding in it some new view, or light, or suggestion
that I have not noticed before. That is the best characteristic of a
thorough and profound book; and I believe this feature of the "Origin of
Species" explains why so many persons have ventured to pass judgment and
criticisms upon it which are by no means worth the paper they are written
on.
Before concluding these lectures there is one point to which I must
advert--though, as Mr. Darwin has said nothing about man in his book, it
concerns myself rather than him;--for I have strongly maintained on sundry
occasions that if Mr. Darwin's views are sound, they apply as much to man
as to the lower mammals, seeing that it is perfectly demonstrable that the
structural differences which separate man from the apes are not greater
than those which separate some apes from others. There cannot be the
slightest doubt in the world that the argument which applies to the
improvement of the horse from an earlier stock, or of ape from ape, applies
to the improvement of man from some simpler and lower stock than man. There
is not a single faculty--functional or structural, moral, intellectual, or
instinctive, there--is no faculty whatever that is not capable of
improvement; there is no faculty whatsoever which does not depend upon
structure, and as structure tends to vary, it is capable of being improved.
Well, I have taken a good deal of pains at various times to prove this, and
I have endeavoured to meet the objections of those who maintain, that the
structural differences between man and the lower animals are of so vast a
character and enormous extent, that even if Mr. Darwin's views are correct,
you cannot imagine this particular modification to take place. It is, in
fact, an easy matter to prove that, so far as structure is concerned, man
differs to no greater extent from the animals which are immediately below
him than these do from other members of the same order. Upon the other
hand, there is no one who estimates more highly than I do the dignity of
human nature, and the width of the gulf in intellectual and moral matters
which lies between man and the whole of the lower creation.
But I find this very argument brought forward vehemently by some. "You say
that man has proceeded from a modification of some lower animal, and you
take pains to prove that the structural differences which are said to exist
in his brain do not exist at all, and you teach that all functions,
intellectual, moral, and others, are the expression or the result, in the
long run, of structures, and of the molecular forces which they exert." It
is quite true that I do so.
"Well, but," I am told at once, somewhat triumphantly, "you say in the same
breath that there is a great moral and intellectual chasm between man and
the lower animals. How is this possible when you declare that moral and
intellectual characteristics depend on structure, and yet tell us that
there is no such gulf between the structure of man and that of the lower
animals?"
I think that objection is based upon a misconception of the real relations
which exist between structure and function, between mechanism and work.
Function is the expression of molecular forces and arrangements no doubt;
but, does it follow from this, that variation in function so depends upon
variation in structure that the former is always exactly proportioned to
the latter? If there is no such relation, if the variation in function
which follows on a variation in structure may be enormously greater than
the variation of the structure, then, you see, the objection falls to the
ground.
Take a couple of watches--made by the same maker, and as completely alike
as possible; set them upon the table, and the function of each--which is
its rate of going--will be performed in the same manner, and you shall be
able to distinguish no difference between them; but let me take a pair of
pincers, and if my hand is steady enough to do it, let me just lightly
crush together the bearings of the balance-wheel, or force to a slightly
different angle the teeth of the escapement of one of them, and of course
you know the immediate result will be that the watch, so treated, from that
moment will cease to go. But what proportion is there between the
structural alteration and the functional result? Is it not perfectly
obvious that the alteration is of the minutest kind, yet that, slight as it
is, it has produced an infinite difference in the performance of the
functions of these two instruments?
Well, now, apply that to the present question. What is it that constitutes
and makes man what he is? What is it but his power of language--that
language giving him the means of recording his experience--making every
generation somewhat wiser than its predecessor--more in accordance with the
established order of the universe?
What is it but this power of speech, of recording experience, which enables
men to be men--looking before and after and, in some dim sense,
understanding the working of this wondrous universe--and which
distinguishes man from the whole of the brute world? I say that this
functional difference is vast, unfathomable, and truly infinite in its
consequences; and I say at the same time, that it may depend upon
structural differences which shall be absolutely inappreciable to us with
our present means of investigation. What is this very speech that we are
talking about? I am speaking to you at this moment, but if you were to
alter, in the minutest degree, the proportion of the nervous forces now
active in the two nerves which supply the muscles of my glottis, I should
become suddenly dumb. The voice is produced only so long as the vocal
chords are parallel; and these are parallel only so long as certain muscles
contract with exact equality; and that again depends on the equality of
action of those two nerves I spoke of. So that a change of the minutest
kind in the structure of one of these nerves, or in the structure of the
part in which it originates, or of the supply of blood to that part, or of
one of the muscles to which it is distributed, might render all of us dumb.
But a race of dumb men, deprived of all communication with those who could
speak, would be little indeed removed from the brutes. And the moral and
intellectual difference between them and ourselves would be practically
infinite, though the naturalist should not be able to find a single shadow
of even specific structural difference.
But let me dismiss this question now, and, in conclusion, let me say that
you may go away with it as my mature conviction, that Mr. Darwin's work is
the greatest contribution which has been made to biological science since
the publication of the "Regne Animal" of Cuvier, and since that of the
"History of Development," of Von Baer. I believe that if you strip it of
its theoretical part it still remains one of the greatest encyclopaedias of
biological doctrine that any one man ever brought forth; and I believe
that, if you take it as the embodiment of an hypothesis, it is destined to
be the guide of biological and psychological speculation for the next three
or four generations.
END OF VOL. II
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