"If, for instance, it could be shown that artificial mutilation
spontaneously reappears in the offspring with sufficient frequency
to exclude all possibilities of chance, then such proof [i.e. that
acquired characters can be transmitted] would be forthcoming. The
transmission of mutilations has been frequently asserted, and has
been even recently again brought forward, but all the supposed
instances have broken down when carefully examined" (p. 390).
Here, then, we are told that proof of the occasional transmission of
mutilations would be sufficient to establish the fact, but on p. 267
we find that no single fact is known which really proves that
acquired characters can be transmitted, "_for the ascertained facts
which seem to point to the transmission of artificially produced
diseases cannot be considered as proof_." [Italics mine.] Perhaps;
but it was mutilation in many cases that Professor Weismann
practically admitted to have been transmitted when he declared that
Obersteiner had verified Brown-Sequard's experiments.
That Professor Weismann recognizes the vital importance to his own
theory of the question whether or no mutilations can be transmitted
under any circumstances, is evident from a passage on p. 425 of his
work, on which he says: "It can hardly be doubted that mutilations
are acquired characters; they do not arise from any tendency
contained in the germ, but are merely the reaction of the body under
certain external influences. They are, as I have recently expressed
it, purely somatogenic characters--viz. characters which emanate
from the body (soma) only, as opposed to the germ-cells; they are,
therefore, characters that do not arise from the germ itself.
"If mutilations must necessarily be transmitted" [which no one that
I know of has maintained], "or even if they might occasionally be
transmitted" [which cannot, I imagine, be reasonably questioned], "a
powerful support would be given to the Lamarckian principle, and the
transmission of functional hypertrophy or atrophy would thus become
highly probable."
I have not found any further attempt in Professor Weismann's book to
deal with the evidence adduced by Mr. Darwin to show that
mutilations, if followed by diseases, are sometimes inherited; and I
must leave it to the reader to determine how far Professor Weismann
has shown reason for rejecting Mr. Darwin's conclusion. I do not,
however, dwell upon these facts now as evidence of a transmitted
change of bodily form, or of instinct due to use and disuse or
habit; what they prove is that the germ-cells within the parent's
body do not stand apart from the other cells of the body so
completely as Professor Weismann would have us believe, but that, as
Professor Hering, of Prague, has aptly said, they echo with more or
less frequency and force to the profounder impressions made upon
other cells.
I may say that Professor Weismann does not more cavalierly wave
aside the mass of evidence collected by Mr. Darwin and a host of
other writers, to the effect that mutilations are sometimes
inherited, than does Mr. Wallace, who says that, "as regards
mutilations, it is generally admitted that they are not inherited,
and there is ample evidence on this point." It is indeed generally
admitted that mutilations, when not followed by disease, are very
rarely, if ever, inherited; and Mr. Wallace's appeal to the "ample
evidence" which he alleges to exist on this head, is much as though
he should say that there is ample evidence to show that the days are
longer in summer than in winter. "Nevertheless," he continues, "a
few cases of apparent inheritance of mutilations have been recorded,
and these, if trustworthy, are difficulties in the way of the
theory." . . . "The often-quoted case of a disease induced by
mutilation being inherited (Brown-Sequard's epileptic guinea-pigs)
has been discussed by Professor Weismann and shown to be not
conclusive. The mutilation itself--a section of certain nerves--was
never inherited, but the resulting epilepsy, or a general state of
weakness, deformity, or sores, was sometimes inherited. It is,
however, possible that the mere injury introduced and encouraged the
growth of certain microbes, which, spreading through the organism,
sometimes reached the germ-cells, and thus transmitted a diseased
condition to the offspring." {286}
I suppose a microbe which made guinea-pigs eat their toes off was
communicated to the germ-cells of an unfortunate guinea-pig which
had been already microbed by it, and made the offspring bite its
toes off too. The microbe has a good deal to answer for.
On the case of the deterioration of horses in the Falkland Islands
after a few generations, Professor Weismann says:--
"In such a case we have only to assume that the climate which is
unfavourable, and nutriment which is insufficient for horses, affect
not only the animal as a whole but also its germ-cells. This would
result in the diminution in size of the germ-cells, the effects upon
the offspring being still further intensified by the insufficient
nourishment supplied during growth. But such results would not
depend upon the transmission by the germ-cells of certain
peculiarities due to the unfavourable climate, which only appear in
the full-grown horse."
But Professor Weismann does not like such cases, and admits that he
cannot explain the facts in connection with the climatic varieties
of certain butterflies, except "by supposing the passive acquisition
of characters produced by the direct influence of climate."
Nevertheless, in his next paragraph but one he calls such cases
"doubtful," and proposes that for the moment they should be left
aside. He accordingly leaves them, but I have not yet found what
other moment he considered auspicious for returning to them. He
tells us that "new experiments will be necessary, and that he has
himself already begun to undertake them." Perhaps he will give us
the results of these experiments in some future book--for that they
will prove satisfactory to him can hardly, I think, be doubted. He
writes:--
"Leaving on one side, for the moment, these doubtful and
insufficiently investigated cases, we may still maintain that the
assumption that changes induced by external conditions in the
organism as a whole are communicated to the germ-cells after the
manner indicated in Darwin's hypothesis of pangenesis, is wholly
unnecessary for the explanation of these phenomena. Still we cannot
exclude the possibility of such a transmission occasionally
occurring, for even if the greater part of the effects must be
attributable to natural selection, there might be a smaller part in
certain cases which depends on this exceptional factor."
I repeatedly tried to understand Mr. Darwin's theory of pangenesis,
and so often failed that I long since gave the matter up in despair.
I did so with the less unwillingness because I saw that no one else
appeared to understand the theory, and that even Mr. Darwin's
warmest adherents regarded it with disfavour. If Mr. Darwin means
that every cell of the body throws off minute particles that find
their way to the germ-cells, and hence into the new embryo, this is
indeed difficult of comprehension and belief. If he means that the
rhythms or vibrations that go on ceaselessly in every cell of the
body communicate themselves with greater or less accuracy or
perturbation, as the case may be, to the cells that go to form
offspring, and that since the characteristics of matter are
determined by vibrations, in communicating vibrations they in effect
communicate matter, according to the view put forward in the last
chapter of my book Luck or Cunning, then we can better understand
it. I have nothing, however, to do with Mr. Darwin's theory of
pangenesis beyond avoiding the pretence that I understand either the
theory itself or what Professor Weismann says about it; all I am
concerned with is Professor Weismann's admission, made immediately
afterwards, that the somatic cells may, and perhaps sometimes do,
impart characteristics to the germ-cells.
"A complete and satisfactory refutation of such an opinion," he
continues, "cannot be brought forward at present"; so I suppose we
must wait a little longer, but in the meantime we may again remark
that, if we admit even occasional communication of changes in the
somatic cells to the germ-cells, we have let in the thin end of the
wedge, as Mr. Darwin did when he said that use and disuse did a good
deal towards modification. Buffon, in his first volume on the lower
animals, {288} dwells on the impossibility of stopping the breach
once made by admission of variation at all. "If the point," he
writes, "were once gained, that among animals and vegetables there
had been, I do not say several species, but even a single one, which
had been produced in the course of direct descent from another
species; if, for example, it could be once shown that the ass was
but a degeneration from the horse--then there is no farther limit to
be set to the power of Nature, and we should not be wrong in
supposing that with sufficient time she could have evolved all other
organized forms from one primordial type." So with use and disuse
and transmission of acquired characteristics generally--once show
that a single structure or instinct is due to habit in preceding
generations, and we can impose no limit on the results achievable by
accumulation in this respect, nor shall we be wrong in conceiving it
as possible that all specialization, whether of structure or
instinct, may be due ultimately to habit.
How far this can be shown to be probable is, of course, another
matter, but I am not immediately concerned with this; all I am
concerned with now is to show that the germ-cells not unfrequently
become permanently affected by events that have made a profound
impression upon the somatic cells, in so far that they transmit an
obvious reminiscence of the impression to the embryos which they go
subsequently towards forming. This is all that is necessary for my
case, and I do not find that Professor Weismann, after all, disputes
it.
But here, again, comes the difficulty of saying what Professor
Weismann does, and what he does not, dispute. One moment he gives
all that is wanted for the Lamarckian contention, the next he denies
common sense the bare necessaries of life. For a more exhaustive
and detailed criticism of Professor Weismann's position, I would
refer the reader to an admirably clear article by Mr. Sidney H.
Vines, which appeared in Nature, October 24, 1889. I can only say
that while reading Professor Weismann's book, I feel as I do when I
read those of Mr. Darwin, and of a good many other writers on
biology whom I need not name. I become like a fly in a window-pane.
I see the sunshine and freedom beyond, and buzz up and down their
pages, ever hopeful to get through them to the fresh air without,
but ever kept back by a mysterious something, which I feel but
cannot either grasp or see. It was not thus when I read Buffon,
Erasmus Darwin, and Lamarck; it is not thus when I read such
articles as Mr. Vines's just referred to. Love of self-display, and
the want of singleness of mind that it inevitably engenders--these,
I suppose, are the sins that glaze the casements of most men's
minds; and from these, no matter how hard he tries to free himself,
nor how much he despises them, who is altogether exempt?
Finally, then, when we consider the immense mass of evidence
referred to briefly, but sufficiently, by Mr. Charles Darwin, and
referred to without other, for the most part, than off-hand
dismissal by Professor Weismann in the last of the essays that have
been recently translated, I do not see how anyone who brings an
unbiased mind to the question can hesitate as to the side on which
the weight of testimony inclines. Professor Weismann declares that
"the transmission of mutilations may be dismissed into the domain of
fable." {290} If so, then, whom can we trust? What is the use of
science at all if the conclusions of a man as competent as I readily
admit Mr. Darwin to have been, on the evidence laid before him from
countless sources, is to be set aside lightly and without giving the
clearest and most cogent explanation of the why and wherefore? When
we see a person "ostrichizing" the evidence which he has to meet, as
clearly as I believe Professor Weismann to be doing, we shall in
nine cases out of ten be right in supposing that he knows the
evidence to be too strong for him.