按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
tells us； on the first page of his preface； that he has no intention
of dealing even in outline with the vast subject of evolution in
general； and has only tried to give such an account of the theory of
natural selection as may facilitate a clear conception of Darwin's
work。 How far he has succeeded is a point on which opinion will
probably be divided。 Those who find Mr。 Darwin's works clear will
also find no difficulty in understanding Mr。 Wallace； those； on the
other hand； who find Mr。 Darwin puzzling are little likely to be
less puzzled by Mr。 Wallace。 He continues：…
〃The objections now made to Darwin's theory apply solely to the
particular means by which the change of species has been brought
about； not to the fact of that change。〃
But 〃Darwin's theory〃as Mr。 Wallace has elsewhere proved that he
understandshas no reference 〃to the fact of that change〃that is
to say； to the fact that species have been modified in course of
descent from other species。 This is no more Mr。 Darwin's theory
than it is the reader's or my own。 Darwin's theory is concerned
only with 〃the particular means by which the change of species has
been brought about〃； his contention being that this is mainly due to
the natural survival of those individuals that have happened by some
accident to be born most favourably adapted to their surroundings；
or； in other words； through accumulation in the common course of
nature of the more lucky variations that chance occasionally
purveys。 Mr。 Wallace's words； then； in reality amount to this； that
the objections now made to Darwin's theory apply solely to Darwin's
theory； which is all very well as far as it goes； but might have
been more easily apprehended if he had simply said； 〃There are
several objections now made to Mr。 Darwin's theory。〃
It must be remembered that the passage quoted above occurs on the
first page of a preface dated March 1889； when the writer had
completed his task； and was most fully conversant with his subject。
Nevertheless； it seems indisputable either that he is still
confusing evolution with Mr。 Darwin's theory； or that he does not
know when his sentences have point and when they have none。
I should perhaps explain to some readers that Mr。 Darwin did not
modify the main theory put forward； first by Buffon； to whom it
indisputably belongs； and adopted from him by Erasmus Darwin；
Lamarck； and many other writers in the latter half of the last
century and the earlier years of the present。 The early
evolutionists maintained that all existing forms of animal and
vegetable life； including man； were derived in course of descent
with modification from forms resembling the lowest now known。
Mr。 Darwin went as far as this； and farther no one can go。 The
point at issue between him and his predecessors involves neither the
main fact of evolution； nor yet the geometrical ratio of increase；
and the struggle for existence consequent thereon。 Messrs。 Darwin
and Wallace have each thrown invaluable light upon these last two
points； but Buffon； as early as 1756； had made them the keystone of
his system。 〃The movement of nature；〃 he then wrote； 〃turns on two
immovable pivots： one； the illimitable fecundity which she has
given to all species： the other； the innumerable difficulties which
reduce the results of that fecundity。〃 Erasmus Darwin and Lamarck
followed in the same sense。 They thus admit the survival of the
fittest as fully as Mr。 Darwin himself； though they do not make use
of this particular expression。 The dispute turns not upon natural
selection； which is common to all writers on evolution； but upon the
nature and causes of the variations that are supposed to be selected
from and thus accumulated。 Are these mainly attributable to the
inherited effects of use and disuse； supplemented by occasional
sports and happy accidents？ Or are they mainly due to sports and
happy accidents； supplemented by occasional inherited effects of use
and disuse？
The Lamarckian system has all along been maintained by Mr。 Herbert
Spencer； who； in his 〃Principles of Biology；〃 published in 1865；
showed how impossible it was that accidental variations should
accumulate at all。 I am not sure how far Mr。 Spencer would consent
to being called a Lamarckian pure and simple； nor yet how far it is
strictly accurate to call him one； nevertheless； I can see no
important difference in the main positions taken by him and by
Lamarck。
The question at issue between the Lamarckians； supported by Mr。
Spencer and a growing band of those who have risen in rebellion
against the Charles…Darwinian system on the one hand； and Messrs。
Darwin and Wallace with the greater number of our more prominent
biologists on the other； involves the very existence of evolution as
a workable theory。 For it is plain that what Nature can be supposed
able to do by way of choice must depend on the supply of the
variations from which she is supposed to choose。 She cannot take
what is not offered to her； and so again she cannot be supposed able
to accumulate unless what is gained in one direction in one
generation； or series of generations； is little likely to be lost in
those that presently succeed。 Now variations ascribed mainly to use
and disuse can be supposed capable of being accumulated； for use and
disuse are fairly constant for long periods among the individuals of
the same species； and often over large areas； moreover； conditions
of existence involving changes of habit； and thus of organisation；
come for the most part gradually； so that time is given during which
the organism can endeavour to adapt itself in the requisite
respects； instead of being shocked out of existence by too sudden
change。 Variations； on the other hand； that are ascribed to mere
chance cannot be supposed as likely to be accumulated； for chance is
notoriously inconstant； and would not purvey the variations in
sufficiently unbroken succession； or in a sufficient number of
individuals； modified similarly in all the necessary correlations at
the same time and place to admit of their being accumulated。 It is
vital therefore to the theory of evolution； as was early pointed out
by the late Professor Fleeming Jenkin and by Mr。 Herbert Spencer；
that variations should be supposed to have a definite and persistent
principle underlying them； which shall tend to engender similar and
simultaneous modification； however small； in the vast majority of
individuals composing any species。 The existence of such a
principle and its permanence is the only thing that can be supposed
capable of acting as rudder and compass to the accumulation of
variations； and of making it hold steadily on one course for each
species； till eventually many havens； far remote from one another；
are safely reached。
It is obvious that the having fatally impaired the theory of his
predecessors could not warrant Mr。 Darwin in claiming； as he most
fatuously did； the theory of evolution。 That he is still generally
believed to have been the originator of this theory is due to the
fact that he claimed it； and that a powerful literary backing at
once came forward to support him。 It seems at first sight
improbable that those who too zealously urged his claims were
unaware that so much had been written on the subject； but when we
find even Mr。 Wallace himself as profoundly ignorant on this subject
as he still either is； or affects to be； there is no limit
assignable to the ignorance or affected ignorance of the kind of
biologists who would write reviews in leading journals thirty years
ago。 Mr。 Wallace writes：…
〃A few great naturalists； struck by the very slight difference
between many of these species； and the numerous links that exist
between the most different forms of animals and plants； and also
observing that a great many species do vary considerably in their
forms； colours and habits； conceived the idea that they might be all
produced one from the other。 The most eminent of these writers was
a great French naturalist； Lamarck； who published an elaborate work；
the Philosophie Zoologique； in which he endeavoured to prove that
all animals whatever are descended from other species of animals。
He attributed the change of species chiefly to the effect of changes
in the conditions of lifesuch as climate； food； &c。； and
especially to the desires and efforts of the animals themselves to
improve their condition； leading to a modification of form or size
in certain parts； owing to the well…known physiological law that all
organs are strengthened by constant use； while they are weakened or
even completely lost by disuse 。 。 。
〃The only other important work dealing with the question was the
celebrated 'Vestiges of Creation；' published anonymously； but now
acknowledged to have been written by the late Robert Chambers。〃
None are so blind as those who will not see； and it would be waste
of time to argue with the invincible ignorance of one who thinks
Lamarck and Buffon conceived that all species were produced from one
another； more especially as I have already dealt at some length with
the early evolutionists in my work； 〃Evolution； Old and New；〃 first
published ten years ago；