may be set a remark by Dr. Whewell, that ‘the loose and _infantine_
grasp of common language cannot hold objects steadily enough for
scientific examination, or lift them from one stage of generalization
to another. They must be secured by the rigid mechanism of a
scientific phraseology.’ To say that ‘the first vertebrate must have
been the product of innumerable antecedent factors,’ is, perhaps, an
expression more puzzling than if one merely said that ‘its immediate
progenitors’ were ‘a single pair;’ but then it has the advantage
of being considerably more suggestive, and a good deal more to the
purpose. Among these ‘factors’ of a living creature parents commonly
find a place,--two parents generally; in some cases, only one; in some
cases, not even one, if we are to believe the advocates of spontaneous
generation, or the still popular view in regard to the Creation. To
the parental factors of any particular offspring must be added those
which are constituted by food and climate and a multitude of changes
and chances in the whole course of its existence. Some characters it
may derive from remote ancestors, transmitted through, though not
developed in, its ‘immediate progenitors.’ It is now forty years since
two French anatomists showed the possibility, or even probability, of
a connection between the molluscous cuttle-fish and the vertebrate
type; and, considering the propensity of the highest vertebrate for
perpetually squirting ink at those who meddle with it, most readers
of controversy will think the instance well selected. Those who wish
to be told what the first vertebrate was probably like, should first
accurately define what they mean by a vertebrate. Is a jointed backbone
the only essential? And if so, how many vertebræ are essentially
requisite? A creature with two vertebræ would be as much a vertebrate
as a creature with three. What shall we say, then, of a creature
possessing, if we may use the expression, but a single vertebra? It
would not have a jointed backbone. It would not be a vertebrate. Yet,
by the simple multiplication of similar parts, in accordance with a
thousand analogies, a vertebrate could be developed from it. By the
differentiation of these similar parts, which not only might follow,
but must follow, a great variety of species could easily be evolved.
Those who really take an interest in the problems connected with this
subject, and whose ‘convictions’ are not too strong and absolute to be
swayed by ascertained facts and logical reasoning will do well to study
the ‘Principles of Biology,’ Herbert Spencer. They will there see
by what extraordinarily simple gradations the lowliest organisms are
connected with higher and the highest forms. They will there find that
‘modification of characters’ is a doctrine less intricate than might
be supposed, even if it cannot be wholly explained in words of one
syllable.
If any intelligent persons can discern the undulatory theory of light
and the modern system of botany in the first chapter of Genesis, no
one would wish to complain of their ingenuity, unless they proposed to
support a particular theory of inspiration by these discoveries. But
then, if the theories of science are only ‘the undulations of human
opinion,’ it becomes necessary to ask why the botanical undulation of
the present day is accepted as a witness, and the Darwinian undulation
rejected. Had the famous Pagan critic, to whom your correspondent
‘R. T. E.’ refers, imagined the sentence, ‘Let there be light,
and there was light,’ to be a scientific description instead of a
theological one, we may feel sure that he would have condemned it for
bombast instead of praising it for its majesty of expression. As it
is, he does not declare it to be the sublimest sentence ever uttered,
but remarks that ‘the lawgiver of the Jews, no common man, having
comprehended the power of the divinity according to the just conception
of it, unfolded it agreeably thereto,’ both in this and in the parallel
phrase, ‘Let the dry land appear, and it was so.’ That all things which
_are_ and which _become_, both are what they are and become what they
become by the simple fiat of the supreme God, is a piece of elementary
philosophy and religion, which, I conceive, Sir, none of your
correspondents can have any wish to dispute; but that the writer of
Genesis anticipated by his scientific knowledge the epoch of Copernicus
and Newton, Young and Fresnel, Linnæus, De Jussieu and Cuvier, is not
only not proven by the few simple phrases of his writings that have
anything remotely to do with the branches of science which they so
nobly illustrated; much more than this, it would be a disgrace and
heavy imputation upon him had he known all _they_ believed, and yet
expressed himself so badly as to leave the world for thousands of years
in ignorance of the very germs of the true theories, so obscurely
that no one should ever have dreamed that he was alluding to the true
theories till after they had been independently discovered.
Your correspondent ‘Xn’ will find both his pleasure and his profit in
reading the chapter on Instinct in ‘Darwin’s Origin of Species.’ It
will give him some idea, I say not, how the reasoning faculty was first
acquired, but how it may have been gradually developed. By a careful
study of the same work he, and many others who need the knowledge, will
see that in accordance with Darwinism the deterioration of a species is
quite possible. His quaintly expressed argument about Adam’s ‘immediate
progenitor’ omits to notice that in the moral world it is a step
upward to become capable of sinning, just as in the physical world it
is a step upward to become capable of dying, so that the wretchedest
man with reason is higher in the scale than the noblest dog, and the
humblest plant than the costliest and most beautiful stone. The other
difficulty which he puts forward of an abrupt transition between the
first man with reason and the parents of such a man without reason is a
difficulty, like that in regard to the first vertebrate, one of words
rather than of facts. As with the origin of language and of languages,
as with the origin of the natural kingdoms and of every individual form
of life, so with the origin of reason; could we see the whole series of
steps, with their infinitely numerous and sometimes almost infinitely
fine and subtle points of discrimination, we should probably be unable
to fix upon any one definite division and say, here noise ends and
articulate language begins; or, here Saxon ends and English begins; or,
_this_ is the top of instinct, and _this_ the dawn of reason.
OYSTERS OF THE CHALK, AND THE THEORY OF DEVELOPMENT.[65]
The interesting notice in your last number, of M. Coquand’s ‘Oysters of
the Chalk,’ draws inferences unfavourable to the theory of development
or evolution which scarcely seem warranted by the facts. It need not be
‘difficult to imagine the creature as existing under such conditions,
that one species, while engaged in “the struggle for existence,” should
starve out and extinguish another;’ for however widely we may find
a fossil species dispersed, it is not probable that it occupied the
whole of its territory at one and the same time, and in the limited
area occupied immediately before its extinction, new varieties may
have prevailed over and displaced the old by some slightly superior
adaptation to the food-supply of the region. The extinction of
any particular species may in some instances have been due to the
extinction, or loss by other means, of its own appropriate food.
Again, it is not necessary to suppose that the hinge, or the internal
or external structure of the shell of an oyster, has been altered by
what may be called the direct action of ‘natural selection,’ since by
the well-established principle of ‘correlation’ the variation in one
part of an organism is nearly or quite certain to produce variations
in other parts. ‘If any such change did occur,’ it is argued, ‘it must
have been _per saltum_, since with these mollusks, numerous as they
are, there are no forms that can fairly be recognised as transitional.’
But this appeal to the evidence of facts is somewhat premature. The
immense difference pointed out between the geological records of
England and France in regard to these very oysters of the chalk,
leaves it perfectly open for us to suppose that even the comparatively
full French record is itself exceedingly imperfect, and that the
transitional forms have either not been preserved, or remain yet to be
discovered. Mr. Darwin gives reasons for believing that when variation
once begins it continues with some vigour; hence, between two settled
wide-spread species connected genealogically together we might expect a
large number of transitional varieties, each represented by only a few
individuals, so that the whole number of these transitional forms might
well be lost to the genealogical record.
Finally, the objection from the scarcity of oysters at the present
day, compared with the great abundance of species in the past, does
not really touch the theory of development, which is concerned to
explain how species come into existence, not how they go out of it.
That varieties, species, genera, have been superseded or extinguished,
within longer or shorter periods, is a fact admitted on all hands.
The general principle of natural selection will account for this in
the rough, maintaining as it does that fresh varieties, species, and
genera better adapted to the surrounding circumstances have arisen,
and by their superior adaptation unavoidably ousted the older forms.
Digging down into the records of history we find a time when the
Romans were supreme in the civilized world; no two consecutive years
of the interval present any remarkable divergence of the prevailing
conditions, yet now we may say of that Roman supremacy in the civilized
world, that, ‘like the Mastodon, it is a thing of the past.’
Torquay, May 14, 1870.
THE MATHEMATICAL TEST OF NATURAL SELECTION.[66]
The soul of many an anti-Darwinian will have been cheered by Mr. A. W.
Bennett’s paper on ‘The Theory of Natural Selection from a Mathematical
Point of View.’ It is, in fact, a very admirable piece of special
pleading, based on a skilful assumption of premisses which, to a
careless or biassed observer, might seem indisputable.
The tendency to variation is spoken of as something very mysterious, of
which no adequate account has ever yet been given. Yet the very simple
explanation is no bad one,--that where two parents are concerned in
the production of any offspring, the product in part resembling each
of the producers must of necessity also in part differ from each of
them. Between the parents themselves, Mr. Herbert Spencer has shown
that differences of age and external circumstances would ensure the
requisite want of resemblance in the absence of any other cause.
‘The rigid test of mathematical calculation’ is then applied to the
case of mimetic butterflies, with the view of showing that they could
not have been produced simply according to the laws of variation,
inheritance, and natural selection. In the application of this rigid
test, the very first step is a perfectly gratuitous assumption, ‘that
it would require, at the very lowest calculation, one thousand steps
to enable the normal _Leptalis_ to put on its protective form.’ Who is
to prove that fifty differences would be insufficient? An interval of
a thousand years might be granted for establishing each one of these
variations. Suppose even fifty thousand, instead of only fifty steps,
to be necessary, it is another gratuitous assumption that ‘the smallest
change in the direction of the _Ithomia_, which we can conceive on any
hypothesis to be beneficial to the _Leptalis_, is at the very lowest
one-fiftieth of the change required to produce perfect resemblance.’
How small a difference must decide the choice made by a donkey placed
equidistant between two bundles of hay! Certainly, then, a bird on the
wing, having to choose amidst myriads of butterflies, may be determined
by an almost infinitesimal distinction. Further, though the whole
change may be produced by an immense number of small changes, it is not
necessary to suppose that all the changes will be equally small. It
is merely begging the question to assume that the first change could
not possibly be large enough to be of any use. And if it may be of
use, the whole mathematical calculation, based on its being useless,
breaks down from the beginning. Again, since the _Leptalis_ may have
spent one million years in arriving at its present likeness to the
present _Ithomia_, it is impossible to assert that the normal forms
of the two butterflies were as wide apart at the beginning of that
period as they are at present. The mimicry having once set in, might be
retained by parallel variations. This, indeed, cannot fail to be the
case, if the protection is to be a lasting one; for when the _Ithomia_
varies in outward appearance, unless the _Leptalis_ varies in the same
direction, the resemblance will be lost. This progressive mimicry
would be more valuable than an imitation in which no changes occurred,
since the enemies of a mimetic species would in time become aware of
a fraud which had no variations at its command, as birds are said
now-a-days to pounce without hesitation upon caterpillars which very
much resemble twigs[67]. Even ‘a rough imitation’ may be useful in the
first instance, and yet when hostile eyes have long been exercised, and
have acquired greater and greater sharpness, finally nothing less than
_absolute identity_ of appearance may be thoroughly effective. Thus
the perfecting of the resemblance will be no ‘mere freak of Nature,’
nor shall we be ‘landed in the dilemma that the _last_ stages are
comparatively useless’ in this procedure.
The array of figures brought forward to prove that the _Leptalis_
could not have made twenty steps of variation in the direction of the
_Ithomia by chance_, would be much to the purpose if any exponent of
the theory of Natural Selection had ever argued or supposed that
it could. The calculation takes it for granted that the theory is
erroneous, instead of proving it to be in error. Upon this assumption,
it might have been put far more strongly, only that a stronger way
of putting it would have borne on the face of it the suspicion of
some inherent fallacy. It begins by supposing that there are ‘twenty
different ways in which a _Leptalis_ may vary, only one of these being
in the direction ultimately required;’ it might quite as truthfully,
or even more so, have said a thousand instead of twenty, and then the
second step would have given the chance as only one in a million,
instead of one in four hundred. But while the theory of Natural
Selection speaks of numerous minute useful variations, Mr. Bennett
will not allow that combination of terms. Let them be numerous and
minute, if you will, he says; but if small, they cannot be useful; if
useful, they cannot be small. He claims to have Mr. Darwin’s own word
for it, that a large variation would not be permanent, as though Mr.
Darwin had said, ‘living creatures have come to be what they are by
successive useful deviations of structure permanently propagated, but
no large deviations are permanent, and no small ones are useful.’ It
is quite obvious that in the use of relative terms, such as great and
small, Mr. Darwin neither intended to stultify himself nor has done
so. A thing may be large enough to be useful without being large as
compared with something twenty times its own size; and a man may be
said to have a huge brain in a very small body, although the body in
solid content far exceeds the brain. When Mr. Darwin says that ‘Natural
Selection always acts with extreme slowness’, he does not imply that
its steps must therefore be so numerous as to be too small to confer
any advantage. This would be a contradiction in terms. But the steps
may be exceedingly small notwithstanding, and also sometimes separated
by enormous intervals of time from one another.
In introducing his own explanation of things, Mr. Bennett affirms that
‘resemblances, and resemblances of the most wonderful and perfect kind’
in the vegetable kingdom, ‘are in no sense mimetic or protective.’ This
may be so, but it can hardly be said to be proved. When he speaks of
‘man’s reason’ having ‘assisted him so to modify his body as to adapt
himself to the circumstances with which he is surrounded,’ and suggests
that the instinct of animals may have assisted them also to modify
their bodies by slow and gradual degrees to the same purpose, it is
difficult to imagine the process intended, and still more difficult to
see how ‘the slow and gradual degrees’ will escape the rigid test of
mathematical calculation which Mr. Bennett has elsewhere applied; for
if the steps are great, they ought not to be permanent; and if small,
they ought not to be useful. A theory which makes it possible for a
bee to ‘modify its proboscis’ by instinct, or for a man to treat his
nose in the same manner by reason, seems harder of digestion than the
Darwinian.
Torquay, Nov. 12, 1870.
THE GENESIS OF SPECIES.
A review in ‘Nature,’ by Mr. A. W. Bennett, of Mr. Mivart’s ‘Genesis of
Species,’ contains the following passage:--
‘It behoves, therefore, every Darwinian to satisfy himself that either
Mr. Mivart’s premisses or his line of argument is unsound.
‘The objections brought forward by the author are summed up as
follows:--(1) That Natural Selection is incompetent to account for the
incipient stages of useful structures. (2) That it does not harmonize
with the coexistence of closely similar structures of diverse origin.
(3) That there are grounds for thinking that specific differences may
be developed suddenly instead of gradually. (4) That the opinion that
species have definite though different limits to their variability is
still tenable. (5) That certain fossil transitional forms are absent
which might have been expected to be present. (6) That some facts of
geological distribution supplement other difficulties. (7) That the
objection drawn from the physiological difference between “species”
and “races” still exists unrefuted. (8) That there are many remarkable
phenomena in organic forms upon which Natural Selection throws no
light whatever, but the explanations of which, if they could be
attained, might throw light upon specific origination.
‘If these objections are not new, they are at least sustained by new
arguments. They are evidently of very unequal value. The third is very
difficult of proof or disproof. The fifth may be true in our present
state of knowledge, but would be very unsafe by itself as the basis of
an argument. The first, second, and eighth are of greatest value, and
are those which Mr. Mivart has most closely worked out[68].’
The review containing the above passage did not appear till the
present volume was on the very eve of publication. Even a hasty glance
at Mr. Mivart’s book is sufficient to show that Mr. Bennett has not
over-estimated its importance and value. It is scarcely possible here
to do more than make a few reflections upon its general scope, in reply
to the challenge offered to Darwinians. The first objection, as it
stands in the summary, wears the appearance of a misconception. It is
almost certain to produce one. When Mr. Darwin attributes the origin
of species to Natural Selection, he includes expressly, and where not
expressly, by obvious implication, the principle of Variability. He
never maintains that the first or any subsequent stage of a useful
structure can be produced by Natural Selection. Natural Selection
only operates to preserve. Without Variation it would have no sphere
in which to operate, so that from one point of view Mr. Darwin may
be said to attribute the origin of species to Variation rather than
Natural Selection. He is, moreover, far from ignoring the influence
of other principles, such as Inheritance, Reversion, and Correlation,
upon the total result. He may be thought inconsistent with himself in
laying stress at times upon the minuteness of the variations which he
supposes to have slowly accumulated into specific differences, and at
other times admitting the sudden appearance of variations which may
be considered as large ones, and which are certainly striking. But in
the first instance the great and almost overwhelming difficulty was to
induce a belief that forms specifically different could be connected
with one another by descent. By showing that a multitude of small
differences accumulated would make a large total difference, he made
as it were a bridge for the existing incredulity. It now appears that
the gulf may be passed with easy strides instead of the little slow
steps at first thought necessary. This fortifies the doctrine of the
Transmutation of Species, in proportion as there are fewer ‘missing
links,’ fewer transitional forms that need to be accounted for.
Of ‘the coexistence of closely similar structures of diverse origin,’
illustrated so forcibly by the instance of the eye, ‘in at least
three independent lines of descent, the Mollusca, the Annulosa, and
the Vertebrata,’ it can scarcely be denied that Natural Selection
alone would be an inadequate explanation. But here again it should
be observed that Darwinism does not attribute everything to Natural
Selection. It assumes, what must be allowed, that variations occur. In
obedience to what laws those variations themselves are produced is an
interesting speculation, and a most important subject of inquiry. That
such laws or conditions of Variation exist no one can doubt, unless he
has been seduced by Ovidian metamorphoses to believe in trees bleeding
human blood and human foreheads branching with the antlers of the stag.
A knowledge of those conditions might fully explain the coexistence of
similar structures of diverse origin, consistently with the principle
of Natural Selection. The ignorance of them is scarcely a proof that
such coexistence does not harmonize with it.
The objection that giraffes, which profited by long necks in a time
of drought, would find them a disadvantage subsequently, as requiring
a greatly increased size and strength of muscles to support them,
overlooks the law of correlation, by assuming that the elongated neck
would be out of proportion to the other conditions of the creature’s
fabric.
Mr. Mivart’s fourth objection seems at least an extremely improbable
opinion. He refers to Mr. Darwin’s expression, that the goose appears
to have a highly inflexible organization, as if he himself thought
it possible for a species at length to attain to an organization
completely inflexible. Such a view would imply two parents exactly like
one another, producing offspring exactly like themselves; and of such
exact likenesses no known families afford examples.
The seventh objection recalls the still unexplained physiological
difference between ‘species’ and ‘races,’ unions between the former
being sterile, and between the latter fertile. In this branch of the
subject there is much scope still for inquiry. Some of the difficulty
may be due to a trick played us by language. True species have been
defined to be those that are not fertile together; and from the
definition it follows that races which _are_ fertile together are
not true species. But the question is obscured by the use of the two
different words ‘races’ and ‘species,’ the real issue being, whether
races that are and races that are not fertile together can originate
in the same way. The subject in its other bearings has been largely
discussed by Mr. Darwin in his work on ‘Animals and Plants under
Domestication.’