第 38 节
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about it that will shortly prove unanswerable。 We cannot so test
every sixpence given us in change as to be sure that we never take a
bad one; and had better sometimes be cheated than reduce caution to
an absurdity。 Moreover; we have seen from the evidence given in my
preceding article that the germ…cells issuing from a parent's body
can; and do; respond to profound impressions made on the somatic…
cells。 This being so; what impressions are more profound; what
needs engage more assiduous attention than those connected with
self…protection; the procuring of food; and the continuation of the
species? If the mere anxiety connected with an ill…healing wound
inflicted on but one generation is sometimes found to have so
impressed the germ…cells that they hand down its scars to offspring;
how much more shall not anxieties that have directed action of all
kinds from birth till death; not in one generation only but in a
longer series of generations than the mind can realise to itself;
modify; and indeed control; the organisation of every species?
I see Professor S。 H。 Vines; in the article on Weismann's theory
referred to in my preceding article; says Mr。 Darwin 〃held that it
was not the sudden variations due to altered external conditions
which become permanent; but those slowly produced by what he termed
'the accumulative action of changed conditions of life。'〃 Nothing
can be more soundly Lamarckian; and nothing should more conclusively
show that; whatever else Mr。 Darwin was; he was not a Charles…
Darwinian; but what evidence other than inferential can from the
nature of the case be adduced in support of this; as I believe;
perfectly correct judgment? None know better than they who clamour
for direct evidence that their master was right in taking the
position assigned to him by Professor Vines; that they cannot
reasonably look for it。 With us; as with themselves; modification
proceeds very gradually; and it violates our principles as much as
their own to expect visible permanent progress; in any single
generation; or indeed in any number of generations of wild species
which we have yet had time to observe。 Occasionally we can find
such cases; as in that of Branchipus stagnalis; quoted by Mr。
Wallace; or in that of the New Zealand Kea whose skin; I was assured
by the late Sir Julius von Haast; has already been modified as a
consequence of its change of food。 Here we can show that in even a
few generations structure is modified under changed conditions of
existence; but as we believe these cases to occur comparatively
rarely; so it is still more rarely that they occur when and where we
can watch them。 Nature is eminently conservative; and fixity of
type; even under considerable change of conditions; is surely more
important for the well…being of any species than an over…ready power
of adaptation to; it may be; passing changes。 There could be no
steady progress if each generation were not mainly bound by the
traditions of those that have gone before it。 It is evolution and
not incessant revolution that both parties are upholding; and this
being so; rapid visible modification must be the exception; not the
rule。 I have quoted direct evidence adduced by competent observers;
which is; I believe; sufficient to establish the fact that offspring
can be and is sometimes modified by the acquired habits of a
progenitor。 I will now proceed to the still more; as it appears to
me; cogent proof afforded by general considerations。
What; let me ask; are the principal phenomena of heredity? There
must be physical continuity between parent; or parents; and
offspring; so that the offspring is; as Erasmus Darwin well said; a
kind of elongation of the life of the parent。
Erasmus Darwin put the matter so well that I may as well give his
words in full; he wrote:…
〃Owing to the imperfection of language the offspring is termed a new
animal; but is in truth a branch or elongation of the parent; since
a part of the embryon animal is; or was; a part of the parent; and
therefore; in strict language; cannot be said to be entirely new at
the time of its production; and therefore it may retain some of the
habits of the parent system。
〃At the earliest period of its existence the embryon would seem to
consist of a living filament with certain capabilities of
irritation; sensation; volition; and association; and also with some
acquired habits or propensities peculiar to the parent; the former
of these are in common with other animals; the latter seem to
distinguish or produce the kind of animal; whether man or quadruped;
with the similarity of feature or form to the parent。〃 {39}
Those who accept evolution insist on unbroken physical continuity
between the earliest known life and ourselves; so that we both are
and are not personally identical with the unicellular organism from
which we have descended in the course of many millions of years;
exactly in the same way as an octogenarian both is and is not
personally identical with the microscopic impregnate ovum from which
he grew up。 Everything both is and is not。 There is no such thing
as strict identity between any two things in any two consecutive
seconds。 In strictness they are identical and yet not identical; so
that in strictness they violate a fundamental rule of strictness
namely; that a thing shall never be itself and not itself at one and
the same time; we must choose between logic and dealing in a
practical spirit with time and space; it is not surprising;
therefore; that logic; in spite of the show of respect outwardly
paid to her; is told to stand aside when people come to practice。
In practice identity is generally held to exist where continuity is
only broken slowly and piecemeal; nevertheless; that occasional
periods of even rapid change are not held to bar identity; appears
from the fact that no one denies this to hold between the
microscopically small impregnate ovum and the born child that
springs from it; nor yet; therefore; between the impregnate ovum and
the octogenarian into which the child grows; for both ovum and
octogenarian are held personally identical with the newborn baby;
and things that are identical with the same are identical with one
another。
The first; then; and most important element of heredity is that
there should be unbroken continuity; and hence sameness of
personality; between parents and offspring; in neither more nor less
than the same sense as that in which any other two personalities are
said to be the same。 The repetition; therefore; of its
developmental stages by any offspring must be regarded as something
which the embryo repeating them has already done once; in the person
of one or other parent; and if once; then; as many times as there
have been generations between any given embryo now repeating it; and
the point in life from which we startedsay; for example; the
amoeba。 In the case of asexually and sexually produced organisms
alike; the offspring must be held to continue the personality of the
parent or parents; and hence on the occasion of every fresh
development; to be repeating something which in the person of its
parent or parents it has done once; and if once; then any number of
times; already。
It is obvious; therefore; that the germ…plasm (or whatever the fancy
word for it may be) of any one generation is as physically identical
with the germ…plasm of its predecessor as any two things can be。
The difference between Professor Weismann and; we will say;
Heringians consists in the fact that the first maintains the new
germ…plasm when on the point of repeating its developmental
processes to take practically no cognisance of anything that has
happened to it since the last occasion on which it developed itself;
while the latter maintain that offspring takes much the same kind of
account of what has happened to it in the persons of its parents
since the last occasion on which it developed itself; as people in
ordinary life take of things that happen to them。 In daily life
people let fairly normal circumstances come and go without much heed
as matters of course。 If they have been lucky they make a note of
it and try to repeat their success。 If they have been unfortunate
but have recovered rapidly they soon forget it; if they have
suffered long and deeply they grizzle over it and are scared and
scarred by it for a long time。 The question is one of cognisance or
non…cognisance on the part of the new germs; of the more profound
impressions made on them while they were one with their parents;
between the occasion of their last preceding development; and the
new course on which they are about to enter。 Those who accept the
theory put forward independently by Professor Hering of Prague
(whose work on this subject is translated in my book; 〃Unconscious
Memory〃) {40} and by myself in 〃Life and Habit;〃 {41} believe in
cognizance; as do Lamarckians generally。 Weismannites; and with
them the orthodoxy of English science; find non…cognisance more
acceptable。
If the Heringian view is accepted; that heredity is only a mode of
memory; and an extension of memory from one generation to another;
then the repetition of