THE PROBLEMS PRESENTED.
In his classical work on Heredity, Professor J. Arthur Thomson exhausts
the evidence on Lamarckism available then (1908) in a manner worthy of
the summing-up of an English judge. This is presented to the jury of
the biological world and they are still considering it. Their verdict
and his sentence are not yet delivered, and it may be they will still
be long delayed. One might almost use the words of Professor Bateson,
previously quoted, “on our present knowledge the matter is talked out.”
I will make one prophecy in this volume and predict that the fourth
edition of this work in 1930 will contain the verdict of the jury and
sentence of the distinguished judge to the effect that in the case
Lamarck _v._ Weismann the plaintiff has won. As in the Great War the
Old Contemptibles held their line with the utmost difficulty against
the disciplined hosts of the greatest army ever known till then, and
yet the latter found their First Battle of the Marne, so perchance it
may be in the present struggle.
I introduce this chapter with an important passage from the above work
on the _Logical position of the Argument_, in which the two possible
methods of establishing the affirmative position of Lamarck are given;
these are, first, actual experimental proof of transmission, and,
second, a collection of facts which cannot be interpreted without
the hypothesis of modification inheritance. The words are:[28] “_The
neo-Lamarckians have to show that the phenomena they adduce as
illustrations of modification-inheritance cannot be interpreted as the
results of selection operating on germinal variations. In order to do
this to the satisfaction of the other side, the neo-Lamarckians must
prove that the characters in question are outside the scope of natural
selection, that they are non-utilitarian and not correlated with any
useful characters--a manifestly difficult task. The neo-Darwinians, on
the other hand, have to prove that the phenomena in question cannot
be the results of modification-inheritance. And this is in most cases
impossible._”[29]
[28] _Heredity_, 1908, p. 240.
[29] I prefer to state the above passage rather than that on
page 179, which is as follows: “The precise question is this:
_Can a structural change in the body, induced by some change in
use or disuse, or by a change in surrounding influence, affect
the germ-cells in such a specific or representative way that the
offspring will through its inheritance exhibit, even in a slight
degree, the modification which the parent acquired?_” (Italics in
original). The question is very precise and important, but I employ
that given above in preference as lending itself better to the line
of inquiry followed here.
I have placed this passage in italics because of its importance from
the point of view of the two problems which I am presenting and would
remark here that if only all the writers had used Professor Thomson’s
term “modifications” instead of “characters” in the statement of this
doctrine much confusion and evasion of plain facts would have been
avoided, and yet such workers as the Mendelians, if deprived of their
clear-cut term “characters” would have been less able to carry on their
studies. To this point of terminology I refer below.[30]
[30] The term “character” derives both from its etymological origin
and its application to biology a double-edged quality. This is of
great value to the study of Mendelism which can only or mainly
work with “unit-characters,” and it also serves the Weismann dogma
well. In both cases the term obliterates the conception of initial
variation, and while serving the purposes of these two great schools
of thought it directs attention away from the early minute and
unimportant stages by which many _germinal_ variations may have
arisen. If it had been coined for the purpose, which it was not, it
would have been a remarkable instance of polemic cunning. It will
be evident in the course of this study of initial variation, that
the accredited and general use of the term “character” begs the
question far too manifestly for the general use of biologists. If
it be retained for the neo-Darwinian and Mendelian provinces there
is nothing to say against it, but I adopt here with pleasure the
alternative term, often used by Professor Thomson, “modification.”
This is wide enough to include the more clear-cut “character” so
long as one makes it clear that the latter is one of the germinal
variations. Further, I hold that his use of the term “transmission”
instead of “inheritance” is the more useful for a wide range
of phenomena. As far as possible I shall employ the expression
“transmission of modifications,” instead of that well-worn but often
sophisticated expression “inheritance of acquired characters.” This
has been subjected by Sir Archdall Reid and Dr. Dixey, to say nothing
of others such as Mr. George Sandeman, to a somewhat bewildering
analysis. Thus the former says, “It follows that the so-called
“acquirements” are innate and “inherited” in precisely the same
manner as the so-called inborn characters.”* Dr. Dixey admits “that
all characters are both acquired and innate”** and goes on to say
that the accepted meaning of the terms was vague, that it led to
confusion, and that it ought to be dropped. For this remark of Dr.
Dixey one may be thankful, but of my friend Sir Archdall Reid I would
ask what he is doing in this galley?
* _Nature_, Vol. 77, Jan. 30th, 1908, p. 293.
** _Nature_, Vol. 77, Feb. 1908, p. 392.
Sir E. Ray Lankester in a letter in _Nature_, 21st March, 1912,
dissented from the mode of treatment of this point by Sir Archdall
Reid and presumably also by Dr. Dixey in the words “It is not, I
think, permissible to say that the normal characters which arise in
response to normal conditions are with equal fitness to be described
as ‘acquired.’” As to what is a normal character and what are normal
conditions there may be much reason for difference of opinion, but I
have said enough of this discussion to show that the terms “acquired”
and “character” would afford a biological Pascal some such food for
criticism as did the term “probable” in his _Provincial Letters_. The
less these two terms are employed the less misunderstanding there
will be of certain problems.
It has been held that “discussing words is often indescribably
tiresome, but it is better than misunderstanding them,” which is most
true.
In a world teeming with the life of plants and animals, and in the
branch of science which seeks to interpret them, where we enter
upon the unknown much sooner than in any other sphere of science,
Weismann has set out to prove or maintain the most stupendous negative
ever framed by the human mind. It would require generations of men
to _prove_ this negative, if it were probable, and his case rests
mainly on the assumed weakness of his opponents. So what is needed
and demanded from the neo-Lamarckians is the production of a few
well-attested and verified facts, and, as he admits himself, then it
must follow as the night the day that his followers will surrender
his characteristic dogma. The more cautious leaders and teachers of
the day say that this has not taken place and ask for facts, more
facts and still more facts, and this attitude is both judicious and
judicial, for example in a teacher so eminent as Professor J. Arthur
Thomson. Scientific men, in such a position as he occupies with grace
and distinction, owe a serious debt of loyalty to ultimate truth and
to the inquiring minds of the young students of to-day and to-morrow.
Those who are in a position of inferior responsibility and honour,
and more freedom, just rank and file members of the Commons’ House
of Parliament, may be pardoned if they do not exhibit an excess of
deference to authority and if they think for themselves.
Two Questions.
There are before the Scientific jury to-day two very vivid questions.
(1) Can modifications in the structure of an individual organism,
occurring as a result of its experience, be transmitted?
(2) What is the cause of variation?
If, as Weismann taught, the answer to No. 1 is in the negative, there
is little use here in trying to answer No. 2, for from the present
point of view the two stand or fall together in the study of Initiative
in Evolution. Such _distributional_ answers to No. 2 as Bateson and de
Vries may offer do not concern my purpose.
If No. 1 be answered in the affirmative it is sufficient for the
purpose of treating initial variations from the Lamarckian standpoint,
for it is hardly conceivable that Nature would neglect so simple and
obvious a method of leading upwards and onwards the organisms that
inhabit a changing world.
It is very clear from what is written on the subject of evolution
to-day that a _point d’appui_ in the process is earnestly desired
by many workers and that Weismann’s dogma stops the way. A very
significant and important remark is made by Professor W. McDougall
in his small book on Physiological Psychology, with reference to the
inheritance of acquired characters, that it is a “proposition which
most biologists at the present time are inclined to deny because they
cannot conceive how such transmission can be effected. Nevertheless the
rejection of this view leaves us with insuperable difficulties when we
attempt to account for the evolution of the nervous system, and there
are no established facts with which it is incompatible.”[31] I am aware
that in the scheme of observed nature there is evidence of no iron
necessity, that the convenience of psychologists should be provided
for, and they, like others of us, have to do the best they can with the
tools and the materials which exist, and I agree with Professor Thomson
in his remark on _Misunderstanding No. 1_, “that our first business
is to find out the facts of the case, careless whether it makes our
interpretation of the history of life more or less difficult,”[32]
but I am persuaded that he will not treat lightly _such_ a statement,
from _such_ a source, on _such_ a subject as that I have quoted from
Professor McDougall. As to his second statement on the same page
“that in the supply of terminal _variations_, whose transmissibility
is unquestioned, there is ample raw material for evolution” it is
important as an opinion, and no more, and there is in the present
connection, an elusiveness about it which prevents one allowing it to
pass. It should be noted that stress is laid upon the term “variations”
and from the context this means congenital full-blown “characters”
such as those that Weismann says are provided in the germ guided by
selection. At any rate, initial modifications are not signified by
Professor Thomson’s remark. So for _evolution_ of forms of life it is
possible the assertion may be true, but apart from distribution of
variations, under the process called amphimixis, some starting point is
required for the initial and wholly useless stages of many variations.
These may or may not become “characters” or adaptive.
[31] _Physiological Psychology_, 1911, p. 156.
[32] _Op. cit._, p. 179.
What the Problems are not.
The ground may be cleared here by saying what our problems are not.
There is no question as to whether Lamarckism or Darwinism represents
the predominant partner in the story of life; there is no question
of the “relative importance of natural selection and the Lamarckian
factors in organic evolution,” though such a question may arise when
once Lamarckism has received its passport from the authorities; but the
time is not yet. Nor is it a question as to the reason why adaptive
modifications are so constantly present in the germ. It is not a
question of Nature _or_ Nurture, but perhaps may be found to be a study
of Nature _and_ Nurture. It is not a question of Mendelian analysis,
nor as to the distribution of either mutations on the one hand, nor of
minute fluctuating variations on the other. The problems are therefore
limited in scope and ambition, and are none the worse for that, as
being better open to correction or support.
The Problems Considered.
It seems but natural to most persons who contemplate with any care the
ever-changing and progressive drama of life in plants and animals that
unquestionably the _dramatis personæ_ by their individual response to
the environments and exercise of their functions must contribute a
share, however small, to their offspring. When first this view presents
itself to their minds they resent as “unnatural” any other possibility.
But, alas! they find that such a conclusion is not permitted in those
regions where alone the white light of science shines. Here the writ of
_a priori_ does not run. The spirit of inquiry makes its challenge to
every presupposition and every assertion in its province--even those
of current science. I have shown that this particular assumption of
the natural man was firmly challenged by Weismann, who was not the
first, but the greatest, biologist to teach that modifications are
not transmitted. Accordingly, agreeable and convenient as it would be
to assume the Lamarckian hypothesis as a working one, it needs in the
present day to be supported by evidence before this can be allowed.
Facts, then, against Weismann’s dogma are demanded and of such a kind
as will satisfy so powerful an advocate of his own views. In passing
it may be remarked again that there is nothing so misleading as facts,
except statistics, and for both sides to bear in mind the warning of a
French writer that in such inquiries as this we should be careful lest
we find the facts for which we are looking.
To meet the conditions laid down in Professor Thomson’s Canon I
propose to describe certain phenomena which are adduced as instances
of modifications in certain mammals whose structure and mode of life
are intimately known, and whose ancestry is little in dispute.[33]
The most convincing of these lines of evidence are those which are
shown to be outside the range of any form of selection, as well as
the _distributional_ factors of Mendel and de Vries. It is well to
enumerate here the six different factors in organic evolution which
might claim a share in the production of such humble phenomena as form
the subject-matter of this volume--they are:
1. Personal Selection of Darwin.
2. Sexual Selection.
3. Histonal or Cellular Selection of Roux.
4. Germinal Selection.
5. Inheritance according to Mendelian principles.
6. Inheritance of Mutations.
[33] With the exception perhaps of the highest of all, for since the
publication of Prof. Woods Jones’ _Arboreal Man_ the question “Who is
Man?” has received a new answer.
There is a somewhat severe and ill-defined condition attached to the
formula in question for it demands that such modifications as will
satisfy the neo-Darwinians shall not be _correlated with any useful
character_.[34] If such a _conditio sine quâ non_ were taken too
literally it would at once foreclose the case as to the possibility of
transmission of modifications at all, the questions of issue ought in
that case never to have been raised--and, _cadit quæstio_. This cannot
be the intention of the biologist who propounds the formula. It could
not reasonably be carried so far as to insist that a modification
arising from a certain habit, active or passive, in an animal, and
which on that account, and on paper, may loosely be said to be
‘correlated’ with it, is to be ruled out. That would be tantamount to
saying for example, that, because an animal must lie down in a certain
attitude when it rests, or walk or run in a certain manner, in other
words that it is useful to exist, certain modifications claimed to be
due to these fundamental parts of existence must be excluded from the
inquiry. The neo-Darwinian is not a critic easy to be entreated, but
_that_ he would not claim. Let me take one example of what I mean. A
short-haired dog will spend a considerable part of its daily life,
and presumably a long line of ancestors did so too, lying with its
forelegs planted in front of its chest and its head either raised in
the air when awake or resting on the upper surface of the forelegs (of
course the familiar attitude of a dog with its body and head curled
up and fore-legs doubled is not referred to here). If the hairy coat
be examined over its neck and jaw, which lie in this attitude, on and
against the forelegs, a remarkable reversal of the direction of the
hairs is found and the outline of this forms an accurate mould of
the surface applied to the forelegs. This is transmitted of course
from previous generations of domestic dogs. A precisely analogous
reversal of the hairs is found on the under or extensor surfaces of
the forelegs, matching with wonderful exactness the area of pressure
of these on the ground, and anyone can see it who has a canine friend
of the fox-terrier type. Long-haired dogs display it less neatly
outlined. An instance such as this cannot be excluded from the evidence
forthcoming because it is correlated with the useful “character” of
lying in a certain attitude. Such a phenomenon, many similar to which
will be seen later, had at any rate an origin _de novo_ at _some time_
in the ancestral stock, and in _some way_. To discover these is part
of my business. The boldest neo-Darwinian will not claim that this
arrangement of a dog’s hair arose by selectional processes within the
germ either in the initial or completed stages.
[34] My italics.
Correlation.
The term “correlation” is somewhat scornfully said by Weismann to be
“unquestionably a fine word,” and it has indeed in biological writings
a very varied set of meanings. I will not vex the reader with a
reference to our old friend Mesopotamia, but mention what Dr. Vernon in
_Variation in Animals and Plants_ says of the term, referring to the
relation between stature and head-index in man: “Such a statement must
vary according to the notion of the observer as to what does and what
does not constitute correlation.”[35] The most approved and precise
meaning of the loose term in question is that associated with the work
of the biometricians, and a few examples from Dr. Vernon’s book will
show how far this conception of correlation is removed from the literal
application of Professor Thomson’s formula. Dr. Vernon treats of such
phenomena as the correlation of the long heads of greyhounds with
length of legs, contrasting them with the shortened heads and legs of
bull-dogs. He describes also the correlation in man between the stature
and length of forearm from elbow to tip of middle finger, correlated
measurements of crabs, of external structures of prawns, the tufts of
Polish fowls correlated with perforations in the skull, also certain
constitutional peculiarities with colour of skin. These few cases are
enough to give an idea of the more precise and fairer acceptation of
the term, but while these form a useful subject for minute study it may
be remarked that they agree also with Lamarckian factors as to their
origin and development. They are much more in line with Darwin’s use of
the word and are strangely reminiscent of the well-known example of the
Irish elk with its great head and horns which was brought forward in
favour of Lamarckism by Herbert Spencer. They breathe an atmosphere of
physiology rather than anatomy, or function than form.
[35] p. 74.
Enough has been said here by way of defining the terms of the issue.
The negative we have to sustain is that the following facts and
observations declare that certain small modifications cannot be
governed by selection and are not correlated with useful characters.
It will be shown later that Professor Thomson’s stringent condition
is not in all of them compiled with, but that, in spite of this, the
probability of their being valid examples of Lamarckism in practice is
immense.