CHARACTERS AS ADAPTIVE AND SPECIFIC (_Concluded_) 251
SUMMARY 274
APPENDIX I. ON PANMIXIA 291
APPENDIX II. ON CHARACTERS AS ADAPTIVE AND SPECIFIC 307
NOTE A TO PAGE 57 333
NOTE B TO PAGE 89 337
LIST OF ILLUSTRATIONS
PAGE
Portrait of George John Romanes _Frontispiece_
Diagram of Prof. Weismann's Theories 43
FIG. 1. Guinea pigs, showing gangrene of ears due to injury of
restiform bodies 118
FIG. 2. Old Irish Pig (after Richardson) 188
FIG. 3. Skulls of Niata Ox and of Wild White Ox 192
FIG. 4. Lower teeth of Orang (after Tomes) 261
CHAPTER I.
INTRODUCTORY: THE DARWINISM OF DARWIN, AND OF THE POST-DARWINIAN
SCHOOLS.
It is desirable to open this volume of the treatise on _Darwin and after
Darwin_ by taking a brief survey of the general theory of descent,
first, as this was held by Darwin himself, and next, as it is now held
by the several divergent schools of thought which have arisen since
Darwin's death.
The most important of the questions in debate is one which I have
already had occasion to mention, while dealing, in historical order,
with the objections that were brought against the theory of natural
selection during the life-time of Darwin[1]. Here, however, we must
consider it somewhat more in detail, and justify by quotation what was
previously said regarding the very definite nature of his utterances
upon the matter. This question is whether natural selection has been the
sole, or but the main, cause of organic evolution.
[1] Part I, pp. 253-256.
Must we regard survival of the fittest as the one and only principle
which has been concerned in the progressive modification of living
forms, or are we to suppose that this great and leading principle has
been assisted by other and subordinate principles, without the
co-operation of which the results, as presented in the animal and
vegetable kingdoms, could not have been effected? Now Darwin's answer to
this question was distinct and unequivocal. He stoutly resisted the
doctrine that natural selection was to be regarded as the only cause of
organic evolution. On the other hand, this opinion was--and still
continues to be--persistently maintained by Mr. Wallace; and it
constitutes the source of all the differences between his views and
those of Darwin. Moreover, up to the time of Darwin's death, Mr. Wallace
was absolutely alone in maintaining this opinion: the whole body of
scientific thought throughout the world being against him; for it was
deemed improbable that, in the enormously complex and endlessly varied
processes of organic evolution, only a single principle should be
everywhere and exclusively concerned[2]. But since Darwin's death there
has been a great revolution of biological thought in favour of Mr.
Wallace's opinion. And the reason for this revolution has been, that his
doctrine of natural selection as the sole cause of organic evolution has
received the corroborative support of Professor Weismann's theory of
heredity--which has been more or less cordially embraced by a certain
section of evolutionists, and which appears to carry the doctrine in
question as a logical corollary, so far, at all events, as adaptive
structures are concerned.
[2] _Contributions to the Theory of Natural Selection_, p. 47.
Now in this opening chapter we shall have to do merely with a setting
forth of Darwin's opinion: we are not considering how far that opinion
ought to be regarded as having been in any measure displaced by the
results of more recent progress. Such, then, being the only matter which
here concerns us, I will supply a few brief quotations, to show how
unequivocally Darwin has stated his views. First, we may take what he
says upon the "Lamarckian factors[3];" and next we may consider what he
says with regard to other factors, or, in general, upon natural
selection not being the sole cause of organic evolution.
[3] So far as we shall be concerned with them throughout this
treatise, the "Lamarckian factors" consist in the supposed
transmission of acquired characters, whether the latter be due
to the direct influence of external conditions of life on the
one hand, or to the inherited effects of use and disuse on the
other. For the phrase "inherited effects of use and disuse," I
shall frequently employ the term "use-inheritance," which has
been coined by Mr. Platt Ball as a more convenient expression.
"Changed habits produce an inherited effect, as in the period of
the flowering of plants when transported from one climate to
another. With animals the increased use or disuse of parts has had
a more marked influence[4]."
[4] _Origin of Species_, 6th ed. p. 8.
"There can be no doubt, from the facts given in this chapter, that
extremely slight changes in the conditions of life sometimes,
probably often, act in a definite manner on our domesticated
productions; and, as the action of changed conditions in causing
indefinite variability is accumulative, so it may be with their
definite action. Hence considerable and definite modifications of
structure probably follow from altered conditions acting during
long series of generations[5]."
[5] _Variation_ &c. 2nd ed. ii. p. 280.
"How, again, can we explain the inherited effects of the use and
disuse of particular organs? The domesticated duck flies less and
walks more than the wild duck, and its limb bones have become
diminished and increased in a corresponding manner in comparison
with those of the wild duck. A horse is trained to certain paces,
and the colt inherits similar consensual movements. The
domesticated rabbit becomes tame from close confinement; the dog,
intelligent from associating with man; the retriever is taught to
fetch and carry; and these mental endowments and bodily powers are
all inherited. Nothing in the whole circuit of physiology is more
wonderful. How can the use or disuse of a particular limb or of the
brain affect a small aggregate of reproductive cells, seated in a
distant part of the body, in such a manner that the being developed
from these cells inherits the characters of either one or both
parents?... In the chapters devoted to inheritance, it was shown
that a multitude of newly acquired characters, whether injurious or
beneficial, whether of the lowest or highest vital importance, are
often faithfully transmitted[6]."
[6] _Variation_ &c. ii. p. 367.
"When discussing special cases, Mr. Mivart passes over the effects
of the increased use and disuse of parts, which I have always
maintained to be highly important, and have treated in my
'Variation under Domestication' at greater length than, as I
believe, any other writer[7]."
[7] _Origin of Species_, p. 176.
So much for the matured opinion of Darwin touching the validity of the
theory of use-inheritance. Turning now to his opinion on the question
whether or not there are yet any further factors concerned in the
process of organic evolution, I think it will be sufficient to quote a
single passage from the _Origin of Species_. The first paragraph of the
"Conclusion" is devoted to a _resume_ of his views upon this matter, and
consists of the following most emphatic words.
"I have now recapitulated the facts and considerations which have
thoroughly convinced me that species have been modified, during a
long course of descent. This has been effected chiefly through the
natural selection of numerous successive, slight, favourable
variations; aided in an important manner by the inherited effects
of the use and disuse of parts; and in an unimportant manner, that
is in relation to adaptive structures, whether past or present, by
the direct action of external conditions, and by variations which
seem to us in our ignorance to arise spontaneously. It appears that
I formerly underrated the frequency and value of these latter forms
of variation, as leading to permanent modifications of structure
independently of natural selection. But as my conclusions have
lately been much misrepresented, and it has been stated that I
attribute the modification of species exclusively to natural
selection, I may be permitted to remark that in the first edition
of this work, and subsequently, I placed in a most conspicuous
position--namely, at the close of the Introduction--the following
words: 'I am convinced that natural selection has been the main,
but not the exclusive means of modification.' This has been of no
avail. Great is the power of steady misrepresentation; but the
history of science shows that fortunately this power does not long
endure."
In the whole range of Darwin's writings there cannot be found a passage
so strongly worded as this: it presents the only note of bitterness in
all the thousands of pages which he has published. Therefore I do not
think it is necessary to supply any further quotations for the purpose
of proving the state of his opinion upon the point in question. But, be
it carefully noted, from this great or radical difference of opinion
between the joint originators of the theory of natural selection, all
their other differences of opinion arise; and seeing that since the
death of Darwin a large number of naturalists have gone over to the side
of Wallace, it seems desirable here to state categorically what these
other or sequent points of difference are. Without at present discussing
them, therefore, I will merely set them out in a tabular form, in order
that a clear perception may be gained of their logical connexion with
this primary point of difference.
|_The Theory of Natural |_The theory of Natural |
|Selection according to |Selection according to |
|Darwin._ |Wallace._ |
| | |
|Natural Selection has been |Natural Selection has been |
|the main means of |the sole means of |
|modification, not excepting |modification, excepting in |
|the case of Man. |the case of Man. |
| | |
|(_a_) Therefore it is a |(_a_) Therefore it is |
|question of evidence |antecedently impossible |
|whether the Lamarckian |that the Lamarckian factors |
|factors have co-operated. |can have co-operated. |
| | |
|(_b_) Neither all species, |(_b_) Not only all species, |
|nor, _a fortiori_, all |but all specific |
|specific characters, have |characters, must |
|been due to natural |necessarily have been due |
|selection. |to natural selection. |
| | |
|(_c_) Thus the principle of |(_c_) Thus the principle of |
|Utility is not of universal |Utility must necessarily be |
|application, even where |of universal application, |
|species are concerned. |where species are |
| |concerned. |
| | |
|(_d_) Thus, also, the |(_d_) Thus, also, the |
|suggestion as to Sexual |suggestion as to Sexual |
|Selection, or any other |Selection, or of any other |
|supplementary cause of |supplementary cause of |
|modification, may be |modification, must be ruled |
|entertained; and, as in the |out; and, as in the case of |
|case of the Lamarckian |the Lamarckian factors, |
|factors, it is a question |their co-operation deemed |
|of evidence whether, or how |impossible. |
|far, they have co-operated. | |
| | |
|(_e_) No detriment arises |(_e_) The possibility--and, |
|to the theory of natural |_a fortiori_ the |
|selection as a theory of |probability--of any |
|the origin of species by |supplementary factors |
|entertaining the |cannot be entertained |
|possibility, or the |without serious detriment |
|probability, of |to the theory of natural |
|supplementary factors. |selection, as a theory of |
| |the origin of species. |
| | |
|(_f_) Cross-sterility in |(_f_) Cross-sterility in |
|species cannot possibly be |species is probably due to |
|due to natural selection. |natural selection[8]. |
[8] This, to the best of my judgement, is the fairest extract that I
can give of Mr. Wallace's most recently published opinions on
the points in question. [In particular as regards (_a_) see
_Darwinism_ pp. 435-6.] But with regard to some of them, his
expression of opinion is not always consistent, as we shall find
in detail later on. Besides, I am here taking Mr. Wallace as
representative of the Neo-Darwinian school, one or other
prominent member of which has given emphatic expression to each
of the above propositions.
As it will be my endeavour in the ensuing chapters to consider the
rights and the wrongs of these antithetical propositions, I may reserve
further quotations from Darwin's works, which will show that the above
is a correct epitome of his views as contrasted with those of Wallace
and the Neo-Darwinian school of Weismann. But here, where the object is
merely a statement of Darwin's theory touching the points in which it
differs from those of Wallace and Weismann, it will be sufficient to set
forth these points of difference in another and somewhat fuller form. So
far then as we are at present concerned, the following are the matters
of doctrine which have been clearly, emphatically, repeatedly, and
uniformly expressed throughout the whole range of Darwin's writings.
1. That natural selection has been the main means of modification.
2. That, nevertheless, it has not been the only means; but has been
supplemented or assisted by the co-operation of other causes.
3. That the most "important" of these other causes has been the
inheritance of functionally-produced modifications (use-inheritance);
but this only because the transmission of such modifications to progeny
must always have had immediate reference to _adaptive_ ends, as
distinguished from merely useless change.
4. That there are sundry other causes which lead to merely useless
change--in particular, "the direct action of external conditions, and
variations which seem to us in our ignorance to arise spontaneously."
5. Hence, that the "principle of utility," far from being of universal
occurrence in the sphere of animate nature, is only of what may be
termed highly general occurrence; and, therefore, that certain other
advocates of the theory of natural selection were mistaken in
representing the universality of this principle as following by way of
necessary consequence from that theory.
6. Cross-sterility in species cannot possibly be due to natural
selection; but everywhere arises as a result of some physiological
change having exclusive reference to the sexual system--a change which
is probably everywhere due to the same cause, although what this cause
could be Darwin was confessedly unable to suggest.
Such, then, was the theory of evolution as held by Darwin, so far as the
points at present before us are concerned. And, it may now be added,
that the longer he lived, and the more he pondered these points, the
less exclusive was the _role_ which he assigned to natural selection,
and the more importance did he attribute to the supplementary factors
above named. This admits of being easily demonstrated by comparing
successive editions of his works; a method adopted by Mr. Herbert
Spencer in his essay on the _Factors of Organic Evolution_.
My object in thus clearly defining Darwin's attitude regarding these
sundry points is twofold.
In the first place, with regard to merely historical accuracy, it
appears to me undesirable that naturalists should endeavour to hide
certain parts of Darwin's teaching, and give undue prominence to others.
In the second place, it appears to me still more undesirable that this
should be done--as it usually is done--for the purpose of making it
appear that Darwin's teaching did not really differ very much from that
of Wallace and Weismann on the important points in question. I myself
believe that Darwin's judgement with regard to all these points will
eventually prove more sound and accurate than that of any of the recent
would-be improvers upon his system; but even apart from this opinion of
my own it is undesirable that Darwin's views should be misrepresented,
whether the misrepresentation be due to any unfavourable bias against
one side of his teaching, or to sheer carelessness in the reading of his
books. Yet the new school of evolutionists, to which allusion has now so
frequently been made, speak of their own modifications of Darwin's
teaching as "pure Darwinism," in contradistinction to what they call
"Lamarckism." In other words, they represent the principles of
"Darwinism" as standing in some kind of opposition to those of
"Lamarckism": the Darwinian principle of natural selection, they think,
is in itself enough to account for all the facts of adaptation in
organic nature. Therefore they are eager to dispense with the Lamarckian
principle of the inherited effects of use and disuse, together with the
direct influence of external conditions of life, and all or any other
causes of modification which either have been, or in the future may
possibly be, suggested. Now, of course, there is no reason why any one
should not hold these or any other opinions to which his own
independent study of natural science may lead him; but it appears to me
that there is the very strongest reason why any one who deviates from
the carefully formed opinions of such a man as Darwin, should above all
things be careful to be absolutely fair in his representations of them;
he should be scrupulously jealous, so to speak, of not letting it appear
that he is unjustifiably throwing over his own opinions the authority of
Darwin's name.
But in the present case, as we have seen, not only do the Neo-Darwinians
strain the teachings of Darwin; they positively reverse those
teachings--representing as anti-Darwinian the whole of one side of
Darwin's system, and calling those who continue to accept that system in
its entirety by the name "Lamarckians." I know it is sometimes said by
members of this school, that in his utilization of Lamarckian principles
as accessory to his own, Darwin was actuated by motives of "generosity."
But a more preposterous suggestion could not well be made. We may
fearlessly challenge any one who speaks or writes in such a way, to show
any other instance where Darwin's great generosity of disposition had
the effect of influencing by one hair's breadth his still greater
loyalty to truth. Moreover, and with special regard to this particular
case, I would point out that in no one of his many allusions to, and
often lengthy discussions of, these so-called Lamarckian principles,
does he ever once introduce the name of Lamarck; while, on the other
hand, in the only places where he does so--whether in his books or in
his now published letters--he does so in order to express an almost
contemptuous dissatisfaction, and a total absence of obligation. Hence,
having regard to the "generosity" with which he always acknowledged
obligations, there can be no reasonable doubt that Darwin was not in the
smallest degree influenced by the speculative writings of Lamarck; or
that, even if Lamarck had never lived, the _Origin of Species_ would
have differed in any single particular from the form in which it now
stands. Finally, it must not be forgotten that Darwin's acceptance of
the theory of use-inheritance was vitally essential to his theory of
Pangenesis--that "beloved child" over which he had "thought so much as
to have lost all power of judging it[9]."
[9] _Life and Letters_, vol. iii. pp. 72 and 75.
What has just been said touching the relations between Darwin's theory
and that of Lamarck, applies with equal force to the relations between
Darwin's theory and any other theory appertaining to evolution which has
already been, or may hereafter be propounded. Yet so greatly have some
of the Neo-Darwinians misunderstood the teachings of Darwin, that they
represent as "Darwinian heresy" any suggestions in the way of factors
"supplementary to," or "co-operative with" natural selection. Of course,
if these naturalists were to avow themselves followers of Wallace,
instead of followers of Darwin, they would be perfectly justified in
repudiating any such suggestions as, _ipso facto_ heretical. But, as we
have now seen, through all his life Darwin differed from Wallace with
regard to this very point; and therefore, unlike Wallace, he was always
ready to entertain "additional suggestions" regarding the causes of
organic evolution--several of which, indeed, he himself supplied. Hence
we arrive at this curious state of matters. Those biologists who of late
years have been led by Weismann to adopt the opinions of Wallace,
represent as anti-Darwinian the opinions of other biologists who still
adhere to the unadulterated doctrines of Darwin. Weismann's _Essays on
Heredity_ (which argue that natural selection is the only possible cause
of adaptive modification) and Wallace's work on _Darwinism_ (which in
all the respects where any charge of "heresy" is concerned directly
contradicts the doctrine of Darwin)--these are the writings which are
now habitually represented by the Neo-Darwinians as setting forth the
views of Darwin in their "pure" form. The result is that, both in
conversation and in the press, we habitually meet with complete
inversions of the truth, which show the state of confusion into which a
very simple matter has been wrought by the eagerness of certain
naturalists to identify the views of Darwin with those of Wallace and
Weismann. But we may easily escape this confusion, if we remember that
wherever in the writings of these naturalists there occur such phrases
as "pure Darwinism" we are to understand pure _Wallaceism_, or the pure
theory of natural selection to the exclusion of any supplementary
theory. Therefore it is that for the sake of clearness I coined, several
years ago, the terms "Neo-Darwinian" and "Ultra-Darwinian" whereby to
designate the school in question.
* * * * *
So much, then, for the Darwinism of Darwin, as contrasted with the
Darwinism of Wallace, or, what is the same thing, of the Neo-Darwinian
school of Weismann. Next we may turn, by way of antithesis, to the
so-called "Neo-Lamarckian" school of the United States. For, by a
curious irony of fate, while the Neo-Darwinian school is in Europe
seeking to out-Darwin Darwin by assigning an exclusive prerogative to
natural selection in both kingdoms of animate nature, the Neo-Lamarckian
school is in America endeavouring to reform Darwinism in precisely the
opposite direction--viz. by transferring the sovereignty from natural
selection to the principles of Lamarck. Without denying to natural
selection a more or less important part in the process of organic
evolution, members of this school believe that much greater importance
ought to be assigned to the inherited effects of use and disuse than was
assigned to these agencies by Darwin. Perhaps this noteworthy state of
affairs, within a decade of Darwin's death, may lead us to anticipate
that his judgement--standing, as it does, between these two
extremes--will eventually prove the most accurate of all, with respect
to the relative importance of these factors of evolution. But, be this
as it may, I must now offer a few remarks upon the present position of
the matter.
In the first place, to any one who (with Darwin and against Weismann)
admits not only the abstract possibility, but an actual working, of the
Lamarckian factors, it becomes difficult to determine, even
approximately, the degrees of value which ought to be ascribed to them
and to natural selection respectively. For, since the results are in
both cases identical in kind (as, adaptive changes of organic types),
where both sets of causes are supposed to be in operation together, we
have no means of estimating the relative shares which they have had in
bringing about these results. Of course there are large numbers of cases
where it cannot possibly be supposed that the Lamarckian factors have
taken any part at all in producing the observed effects; and therefore
in such cases there is almost full agreement among evolutionists in
theoretically ascribing such effects to the exclusive agency of natural
selection. Of such, for instance, are the facts of protective colouring,
of mimicry, of the growth of parts which, although _useful_, are never
_active_ (e.g. shells of mollusks, hard coverings of seeds), and so on.
But in the majority of cases where adaptive structures are concerned,
there is no means of discriminating between the influences of the
Lamarckian and the Darwinian factors. Consequently, if by the
Neo-Lamarckian school we understand all those naturalists who assign any
higher importance to the Lamarckian factors than was assigned to them by
Darwin, we may observe that members of this school differ very greatly
among themselves as to the degree of importance that ought to be
assigned. On the one hand we have, in Europe, Giard, Perrier, and Eimer,
who stand nearer to Darwin than do a number of the American
representatives--of whom the most prominent are Cope, Osborn, Packard,
Hyatt, Brooks, Ryder, and Dall. The most extreme of these is Professor
Cope, whose collection of essays entitled _The Origin of the Fittest_,
as well as his more recent and elaborate monograph on _The Development
of the Hard Parts of the Mammalia_, represent what appears even to some
other members of his school an extravagant estimate of the importance
of Lamarckian principles.
But the most novel, and in many respects the most remarkable school of
what may be termed Anti-selectionists is one which is now (1894) rapidly
increasing both in numbers and in weight, not only in the New World, but
also in Germany, and to a lesser extent, in Great Britain.
This school, without being either Lamarckian or Darwinian (for its
individual members differ widely from one another in these respects)
maintains a principle which it deems of more importance than either
use-inheritance or natural selection. This principle it calls
Self-adaptation. It is chiefly botanists who constitute this school, and
its principal representatives, in regard to authority, are Sachs,
Pfeffer and Henslow.
Apart from topics which are to be dealt with in subsequent chapters, the
only matters of much importance which have been raised in the
Post-Darwinian period are those presented by the theories of Geddes,
Cope, Hyatt, and others, and certain more or less novel ideas set forth
in Wallace's _Darwinism_.
Mr. Geddes has propounded a new theory of the origin of species, which
in his judgement supersedes to a large extent the theory of natural
selection. He has also, in conjunction with Mr. Thomson, propounded a
theory of the origin of sex. For my own part, I cannot see that these
views embody any principles or suggestions of a sufficiently definite
kind to constitute them theories at all. In this respect the views of
Mr. Geddes resemble those of Professors Cope, Hyatt, and others, on what
they term "the law of acceleration and retardation." In all these
cases, so far as I can see, the so-called explanations are not in fact
any explanations; but either a mere re-statement of the facts, or else
an enunciation of more or less meaningless propositions. Thus, when it
is said that the evolution of any given type has been due to the
"acceleration of growth-force" with respect to some structures, and the
"retardation of growth-force" with respect to others, it appears evident
that we have not any real explanation in terms of causality; we have
only the form of an explanation in the terms of a proposition. All that
has been done is to express the fact of evolution in somewhat obscure
phraseology, since the very thing we want to know about this fact
is--What are the causes of it as a fact, or the reasons which have led
to the increase of some of the parts of any given type, and the
concomitant decrease of others? It is merely the facts themselves that
are again presented by saying that the development has been in the one
case accelerated, while in the other it has been retarded[10].
[10] Take, for example, the following, which is a fair epitome of
the whole:--"I believe that this is the simplest mode of
stating and explaining the law of variation; that some forms
acquire something which their parents did not possess; and that
those which acquire something additional have to pass through
more numerous stages than their ancestors; and those which lose
something pass through fewer stages than their ancestors; and
these processes are expressed by the terms 'acceleration' and
'retardation'" (_Origin of the Fittest_, pp. 125, 226, and
297). Even if this be "the simplest mode of _stating_ the law
of variation," it obviously does nothing in the way of
_explaining_ the law.
So much for what may be termed this New World theory of the origin of
species: it is a mere re-statement of the facts. Mr. Geddes' theory, on
the other hand, although more than a mere re-statement of the facts,
appears to me too vague to be of any explanatory service. His view is
that organic evolution has everywhere depended upon an antagonism,
within the limits of the same organism, between the processes of
nutrition and those of reproduction. But although he is thus able
hypothetically to explain certain facts--such as the shortening of a
flower-spike into a composite flower--the suggestion is obviously
inadequate to meet, even hypothetically, most of the facts of organic
evolution, and especially the development of _adaptive_ structures.
Therefore, it seems to me, we may dismiss it even as regards the
comparatively few facts which it might conceivably explain--seeing that
these same facts may be equally well explained by the causes which are
already known to operate in other cases. For it is the business of
natural selection to ensure that there shall nowhere be any needless
expenditure of vital energy, and, consequently, that everywhere the
balance between nutrition and reproduction shall be most profitably
adjusted.
Similarly with respect to the theory of the _Origin of Sex_, I am unable
to perceive even this much of scientific relevancy. As stated by its
authors the theory is, that the female is everywhere "anabolic," as
compared with the male, which is "katabolic." By anabolic is meant
comparative inactivity of protoplasmic change due to a nutritive winding
up of molecular constitution, while by katabolic is meant the opposite
condition of comparative activity due to a dynamic running down of
molecular constitution. How, then, can the _origin_ of sex be explained,
or the _causes_ which led to the differentiation of the sexes be shown
by saying that the one sex is anabolic and the other katabolic? In so
far as these verbal statements serve to express what is said to be a
general fact--namely, that the female sexual elements are less mobile
than the male--they merely serve to re-state this general fact in
terminology which, as the authors themselves observe, is "unquestionably
ugly." But in so far as any question of _origin_ or _causality_ is
concerned, it appears to me that there is absolutely no meaning in such
statements. They belong to the order of merely formal explanations, as
when it is said that the toxic qualities of morphia are due to this drug
possessing a soporific character.
Much the same, in my opinion, has to be said of the Rev. G. Henslow's
theory of the origin of species by what he terms "self-adaptation."
Stated briefly his view is that there is no sufficient evidence of
natural selection as a _vera causa_, while there is very abundant
evidence of adjustments occurring without it, first in individual
organisms, and next, by inheritance of acquired characters, in species.
Now, much that he says in criticism of the selection theory is of
considerable interest as such; but when we pass from the critical to the
constructive portions of his books and papers, we again meet with the
want of clearness in thought between a statement of facts in terms of a
proposition, and an explanation of them in those of causality. Indeed, I
understand from private correspondence, that Mr. Henslow himself admits
the validity of this criticism; for in answer to my questions,--"How
does Self-adaptation work in each case, and why should protoplasm be
able to _adapt itself_ into the millions of diverse mechanisms in
nature?"--he writes. "Self-adaptation does not profess to be a _vera
causa_ at all; for the true causes of variation can only be found in the
answer to your [above] questions, and I must say at once, _these
questions cannot be answered_." That is, they cannot be answered on the
hypothesis of self-adaptation, which is therefore a statement of the
facts of adaptation as distinguished from an explanation of them.
Nevertheless, two things have here to be noted. In the first place, the
statement of facts which Mr. Henslow has collected is of considerable
theoretical importance as tending to show that there are probably causes
of an internal kind (i. e. other than natural selection) which have been
largely concerned in the adaptive modification of plants. And, in the
second place, it is not quite true that the theory of self-adaptation
is, as its author says in the sentences above quoted, a mere statement
of the facts of adaptation, without any attempt at explaining their
causes. For in his published words he does attempt to do so[11]. And,
although I think his attempt is a conspicuous failure, I ought in
fairness to give examples of it. His books are almost exclusively
concerned in an application of his theory to the mechanisms of flowers
for securing their own fertilization. These mechanisms he ascribes, in
the case of entomophylous flowers, to the "thrusts," "strains," and
other "irritations" supplied to the flowers by their insect visitors,
and consequent "reactions" of the vegetable "protoplasm." But no attempt
is made to show why these "reactions" should be of an _adaptive_ kind,
so as to build up the millions of diverse and often elaborate mechanisms
in question--including not only forms and movements, but also colours,
odours, and secretions. For my own part I confess that, even granting to
an ultra-Lamarckian extent the inheritance of acquired characters, I
could conceive of "self-adaptation" alone producing all such innumerable
and diversified adjustments only after seeing, with Cardinal Newman, an
angel in every flower. Yet Mr. Henslow somewhat vehemently repudiates
any association between his theory and that of teleology.
[11] _Floral Structures_ (Internat. Sc. Ser. lxiv. 1888): _The
Making of Flowers_ (Romance of Science Ser. 1891); and Linn.
Soc. Papers 1893-4.
On the whole, then, I regard all the works which are here classed
together (those by Cope, Geddes, and Henslow), as resembling one another
both in their merits and defects. Their common merits lie in their
erudition and much of their criticism, while their common defects
consist on the one hand in not sufficiently distinguishing between mere
statements and real explanations of facts, and, on the other, in not
perceiving that the theories severally suggested as substitutes for that
of natural selection, even if they be granted true, could be accepted
only as co-operative factors, and by no stretch of logic as substitutes.
* * * * *
Turning now to Mr. Wallace's work on _Darwinism_, we have to notice, in
the first place, that its doctrine differs from "Darwinism" in regard to
the important dogma which it is the leading purpose of that work to
sustain--namely, that "the law of utility" is, to all intents and
purposes, universal, with the result that natural selection is virtually
the only cause of organic evolution. I say "to all intents and
purposes," or "virtually," because Mr. Wallace does not expressly
maintain the abstract impossibility of laws and causes other than those
of utility and natural selection; indeed, at the end of his treatise, he
quotes with approval Darwin's judgement, that "natural selection has
been the most important, but not the exclusive means of modification."
Nevertheless, as he nowhere recognizes any other law or cause of
adaptive evolution[12], he practically concludes that, on inductive or
empirical grounds, there _is_ no such other law or cause to be
entertained--until we come to the particular case of the human mind. But
even in making this one particular exception--or in representing that
some other law than that of utility, and some other cause than that of
natural selection, must have been concerned in evolving the mind of
man--he is not approximating his system to that of Darwin. On the
contrary, he is but increasing the divergence, for, of course, it was
Darwin's view that no such exception could be legitimately drawn with
respect to this particular instance. And if, as I understand must be the
case, his expressed agreement with Darwin touching natural selection not
being the only cause of adaptive evolution has reference to this point,
the quotation is singularly inapt.
[12] "The law of correlation," and the "laws of growth," he does
recognize; and shows that they furnish an explanation of the
origin of many characters, which cannot be brought under "the
law of utility."
Looking, then, to these serious differences between his own doctrine of
evolution--both organic and mental--and that of Darwin, I cannot think
that Mr. Wallace has chosen a suitable title for his book; because, in
view of the points just mentioned, it is unquestionable that _Darwinism_
differs more widely from the _Origin of Species_ than does the _Origin
of Species_ from the writings of the Neo-Lamarckians. But, passing over
this merely nominal matter, a few words ought to be added on the very
material question regarding the human mind. In subsequent chapters the
more general question, or that which relates to the range of utility and
natural selection elsewhere will be fully considered.
Mr. Wallace says,--
"The immense interest that attaches to the origin of the human
race, and the amount of misconception which prevails regarding the
essential teachings of Darwin's theory on the question, as well as
regarding my own special views upon it, induce me to devote a final
chapter to its discussion."
Now I am not aware that there is any misconception in any quarter as to
the essential teachings of Darwin's theory on this question. Surely it
is rather the case that there is a very general and very complete
understanding on this point, both by the friends and the foes of
Darwin's theory--so much so, indeed, that it is about the only point of
similar import in all Darwin's writings of which this can be said. Mr.
Wallace's "special views" on the other hand are, briefly stated, that
certain features, both of the morphology and the psychology of man, are
inexplicable by natural selection--or indeed by any other cause of the
kind ordinarily understood by the term natural: they can be explained
only by supposing "the intervention of some distinct individual
intelligence," which, however, need not necessarily be "one Supreme
Intelligence," but some other order of Personality standing anywhere in
"an infinite chasm between man and the Great Mind of the universe[13]."
Let us consider separately the corporeal and the mental peculiarities
which are given as justifying this important conclusion.
[13] _Natural Selection and Tropical Nature_, p. 205; 1891.
The bodily peculiarities are the feet, the hands, the brain, the voice,
and the naked skin.
As regards the feet Mr. Wallace writes, "It is difficult to see why the
prehensile power [of the great toe] should have been taken away,"
because, although "it may not be compatible with perfectly easy erect
locomotion," "how can we conceive that early man, _as an animal_, gained
anything by purely erect locomotion[14]?" But surely it is not difficult
to conceive this. In the proportion that our simian progenitors ceased
to be arboreal in their habits (and there may well have been very good
utilitarian reasons for such a change of habitat, analogous to those
which are known to have occurred in the phylogenesis of countless other
animals), it would clearly have been of advantage to them that their
already semi-erect attitude should have been rendered more and more
erect. To name one among several probabilities, the more erect the
attitude, and the more habitually it was assumed, the more would the
hands have been liberated for all the important purposes of
manipulation. The principle of the physiological division of labour
would thus have come more and more into play: natural selection would
therefore have rendered the upper extremities more and more suited to
the execution of these purposes, while at the same time it would have
more and more adapted the lower ones to discharging the sole function of
locomotion. For my own part, I cannot perceive any difficulty about
this: in fact, there is an admirable repetition of the process in the
ontogeny of our own children[15].
[14] _Ibid._ pp. 197-8.
[15] For an excellent discussion on the ontogeny of the child in
this connexion, see _Some Laws of Heredity_, by Mr. S. S.
Buckman, pp. 290, _et seq._ (Proc. Cotteswold Nat. Field Club,
vol. x. p. 3, 1892).
Next, with regard to the hand, Mr. Wallace says, that it "contains
latent capacities which are unused by savages, and must have been even
less used by palaeolithic man and his still ruder predecessors." Thus,
"it has all the appearance of an organ prepared for the use of civilized
man[16]." Even if this be true, however, it would surely be a dangerous
argument to rely upon, seeing that we cannot say of how much importance
it may have been for early man--or even apes--to have had their power of
manipulation progressively improved. But is the statement true? It
appears to me that if Mr. Wallace had endeavoured to imitate the
manufactures that were practised by "palaeolithic man," he would have
found the very best of reasons for cancelling his statement. For it is
an extremely difficult thing to chip a flint into the form of an
arrow-head: when made, the suitable attachment of it to a previously
prepared arrow is no easy matter: neither a bow nor a bow-string could
have been constructed by hands of much less perfection than our own: and
the slaying of game with the whole apparatus, when it has been
constructed, requires a manual dexterity which we may be perfectly
certain that Mr. Wallace--unless he has practised the art from
boyhood--does not possess.
[16] _loc. cit._ p. 198.
So it is with his similar argument that the human voice is more
"powerful," more "flexible," and presents a greater "range" and
"sweetness" than the needs of savage life can be held to require. The
futility of this argument is self-evident as regards "power." And
although its weakness is not so obvious with respect to the other three
qualities which are named, need we go further than the closely analogous
case of certain birds to show the precariousness of arguing from such
facts of organic nature to the special operation of "a superior
intelligence"? I can hardly suppose that Mr. Wallace will invoke any
such agency for the purpose of explaining the "latent capacities" of the
voice of a parrot. Yet, in many respects, these are even more wonderful
than those of the human voice, albeit in a wild state they are "never
required or used[17]."
[17] For a discussion of this remarkable case, see _Mental Evolution
in Animals_, pp. 222-3. It appears to me that if Mr. Wallace's
argument from the "latent capacities of the voice of Man" is
good for anything, _a fortiori_ it must be taken to prove that,
in the case of the Parrot, "the organ has been prepared in
anticipation" of the amusement which the cultivation of its
latent capacities arouses in "civilized man."
Once more, with regard to the naked skin, it seems sufficient to quote
the following passage from the first edition of the _Descent of Man_.
"The Rev. T. R. Stebbing, in commenting on this view, remarks, that
had Mr. Wallace 'employed his usual ingenuity on the question of
man's hairless skin, he might have seen the possibility of its
selection through its superior beauty, or the health attaching to
superior cleanliness. At any rate it is surprising that he should
picture to himself a superior intelligence plucking the hair from
the backs of savage men (to whom, according to his own account, it
would have been useful and beneficial), in order that the
descendants of the poor shorn wretches might, after many deaths
from cold and damp in the course of many generations,' have been
forced to raise themselves in the scale of civilization through the
practice of various arts, in the manner indicated by Mr.
Wallace[18]."
[18] _Descent of Man_, 1st Ed. ch. xx. (Trans. Dev. Assoc. for
Science, 1890).
To this it may be added that the Chimpanzee "Sally" was largely denuded
of hair, especially on the back, or the part of "man's organization" on
which Mr. Wallace lays special stress, as being in this respect out of
analogy with other mammalia[19].
[19] The late Prof. Moseley informed me that, during his voyage on
the _Challenger_, he had seen many men whose backs were well
covered with hair.--For an excellent discussion of the whole
question, chiefly in the light of embryology, see the paper by
Buckman already alluded to, pp. 280-289. Also, for an account
of an extraordinary hairy race of men, see _Alone with the
Hairy Ainu_, by A. H. Savage Landor, 1893.
Lastly, touching his statement that the brain of savage man is both
quantitatively and qualitatively in advance of his requirements, it is
here also sufficient to refer to Darwin's answer, as given in the
_Descent of Man_. Mr. Wallace, indeed, ignores this answer in his recent
re-publication of the argument; but it is impossible to understand why
he should have done so. To me, at all events, it seems that one out of
several considerations which Darwin advances is alone sufficient to show
the futility of this argument. I allude to the consideration that the
power of forming abstract ideas with the complex machinery of language
as the vehicle of their expression, is probably of itself enough to
account for both the mass and the structure of a savage's brain. But
this leads us to the second division of Mr. Wallace's argument, or that
derived from the mental endowments of mankind.
Here the peculiarities called into evidence are, "the Mathematical
Faculty," "the Artistic Faculties," and "the Moral Sense." With regard
to the latter, he avows himself a member of the intuitional school of
ethics; but does not prove a very powerful advocate as against the
utilitarian[20].
[20] E.g. "The special faculties we have been discussing clearly
point to the existence in man of something which he has not
derived from his animal progenitors--something which we may
best refer to as being of a spiritual essence or nature,
capable of progressive development under favourable conditions.
On the hypothesis of this spiritual nature, superadded to the
animal nature of man, we are able to understand much that is
otherwise mysterious or unintelligible in regard to him,
especially the enormous influence of ideas, principles, and
beliefs over his whole life and action. Thus alone can we
understand the constancy of the martyr, the unselfishness of
the philanthropist, the devotion of the patriot, the enthusiasm
of the artist, and the resolute and persevering search of the
scientific worker after nature's secrets. Thus we may perceive
that the love of truth, the delight in beauty, the passion for
justice, and the thrill of exultation with which we hear of any
act of courageous self-sacrifice, are the workings within us of
a higher nature which has not been developed by means of the
struggle for material existence." (_Darwinism_, p. 474.) I have
quoted this whole paragraph, because it is so inconsistent with
the rest of Mr. Wallace's system that a mere epitome of it
might well have been suspected of error. Given an intellectual
being, howsoever produced, and what is there "mysterious or
unintelligible" in "the enormous influence of ideas,
principles, and beliefs over his whole life and action"? Or
again, if he be also a social being, what is the relevancy of
adducing "the constancy of the martyr," "the unselfishness of
the philanthropist," "the devotion of the patriot," "the love
of truth," "the passion for justice," "the thrill of exultation
when we hear of any act of courageous self-sacrifice," in
evidence _against_ the law of _utility_, or in order to prove
that a "nature" thus endowed has "_not_ been developed by means
of the struggle for existence," when once this struggle has
been transferred from individuals to communities? The whole
passage reads like an ironical satire in favour of "Darwinism,"
rather than a serious argument against it.
It comes, then, to this. According to Mr. Wallace's eventual
conclusion, man is to be separated from the rest of organic nature, and
the steady progress of evolution by natural causes is to be regarded as
stopped at its final stage, because the human mind presents the
faculties of mathematical calculation and aesthetic perception. Surely,
on antecedent grounds alone, it must be apparent that there is here no
kind of proportion between the conclusion and the _data_ from which it
is drawn. That we are not confined to any such grounds, I will now try
to show.
Let it be remembered, however, that in the following brief criticism I
am not concerned with the issue as to whether, or how far, the
"faculties" in question have owed their origin or their development to
_natural selection_. I am concerned only with the doctrine that in order
to account for such and such particular "faculty" of the human mind,
some order of causation must be supposed other than what we call
natural. I am not a Neo-Darwinist, and so have no desire to make
"natural selection" synonymous with "natural causation" throughout the
whole domain of life and of mind. And I quite agree with Mr. Wallace
that, at any rate, the "aesthetic faculty" cannot conceivably have been
produced by natural selection--seeing that it is of no conceivable
life-serving value in any of the stages of its growth. Moreover, it
appears to me that the same thing has to be said of the play instincts,
sense of the ludicrous, and sundry other "faculties" of mind among the
lower animals. It being thus understood that I am not differing from Mr.
Wallace where he imposes "limits" on the powers of natural selection,
but only where he seems to take for granted that this is the same thing
as imposing limits on the powers of natural causation, my criticism is
as follows.
In the first place, it is a psychological fallacy to regard the
so-called "faculties" of mind as analogous to "organs" of the body. To
classify the latter with reference to the functions which they severally
perform is to follow a natural method of classification. But it is an
artificial method which seeks to partition mental _faculty_ into this,
that, and the other mental _faculties_. Like all other purely artificial
classifications, this one has its practical uses; but, also like them,
it is destitute of philosophical meaning. This statement is so well
recognized by psychologists, that there is no occasion to justify it.
But I must remark that any cogency which Mr. Wallace's argument may
appear to present, arises from his not having recognized the fact which
the statement conveys. For, had he considered the mind as a whole,
instead of having contemplated it under the artificial categories of
constituent "faculties," he would probably not have laid any such
special stress upon some of the latter. In other words, he would have
seen that the general development of the human mind as a whole has
presumably involved the growth of those conventionally abstracted parts,
which he regards as really separate endowments. Or, if he should find it
easier to retain the terms of his metaphor, we may answer him by saying
that the "faculties" of mind are "correlated," like "organs" of the
body; and, therefore, that any general development of the various other
"faculties" have presumably entailed a collateral development of the two
in question.
Again, in the second place, it would seem that Mr. Wallace has not
sufficiently considered the co-operation of either well-known natural
causes, which must have materially assisted the survival of the fittest
where these two "faculties" are concerned. For, even if we disregard the
inherited effects of use--which, however, if entertained as possible in
any degree at all, must have here constituted an important
factor,--there remain on the one hand, the unquestionable influences of
individual education and, on the other hand, of the selection principle
operating in the mind itself.
Taking these two points separately, it is surely sufficiently well known
that individual education--or special training, whether of mind or
body--usually raises congenital powers of any kind to a more or less
considerable level above those of the normal type. In other words,
whatever doubt there may be touching the _inherited_ effects of use,
there can be no question touching the immense _developmental_ effects
thereof in the individual life-time. Now, the conditions of savage life
are not such as lead to any deliberate cultivation of the "faculties"
either of the mathematical or aesthetic order. Consequently, as might be
expected, we find both of them in what Mr. Wallace regards as but a
"latent" stage of development. But in just the same way do we find that
the marvellous powers of an acrobat when specially trained from
childhood--say to curve his spine backwards until his teeth can bite his
heels--are "latent" in all men. Or, more correctly, they are _potential
in every child_. So it is with the prodigious muscular development of a
trained athlete, and with any number of other cases where either the
body or the mind is concerned. Why then should Mr. Wallace select the
particular instances of the mathematical and aesthetic powers in savages
as in any special sense "prophetic" of future development in trained
members of civilized races? Although it is true that these "latent
capacities and powers are unused by savages," is it not equally true
that savages fail to use their latent capacities and powers as tumblers
and athletes? Moreover, is it not likewise true that _as_ used by
savages, or as occurring normally in man, such capacities and powers are
no less poorly developed than are those of the "faculties" on which Mr.
Wallace lays so much stress? In other words, are not "latent capacities
and powers" of all kinds more or less equally in excess of anything that
is ever required of them by man in a state of nature? Therefore, if we
say that where mathematics and the fine arts are concerned the potential
capacities of savage man are in some mystical sense "prophetic" of a
Newton or a Beethoven, so in consistency ought we to say that in these
same capacities we discern a similar prophecy of those other uses of
civilized life which we have in a rope-dancer or a clown.
Again, and in addition to this, it should be remembered that, even if we
do suppose any prophecy of this kind where the particular capacities in
question are concerned, we must clearly extend the reference to the
lower animals. Not a few birds display aesthetic feelings in a measure
fairly comparable with those of savages; while we know that some animals
present the germs of a "faculty" of computation[21]. But, it is
needless to add, this fact is fatal to Mr. Wallace's argument as I
understand it--viz. that the "faculties" in question have been in some
special manner communicated by some superior intelligence to _man_.
[21] See _Proc. Zool. Soc._ June 4, 1889, for an account of the
performances in this respect of the Chimpanzee "Sally." Also,
for some remarks on the psychology of the subject, in _Mental
Evolution in Man_, p. 215. I should like to take this
opportunity of stating that, after the two publications above
referred to, this animal's instruction was continued, and that,
before her death, her "counting" extended as far as ten. That
is to say, any number of straws asked for from one to ten would
always be correctly given.
Once more, it is obviously unfair to select such men as a "Newton, a La
Place, a Gauss, or a Cayley" for the purpose of estimating the
difference between savages and civilized man in regard to the latter
"faculty." These men are the picked mathematicians of centuries.
Therefore they are men who not only enjoyed all the highest possible
benefits of individual culture, but likewise those who have been most
endowed with mathematical power congenitally. So to speak, they are the
best variations in this particular direction which our race is known to
have produced. But had such variations arisen among savages it is
sufficiently obvious that they could have come to nothing. Therefore, it
is the _normal average_ of "mathematical faculty" in civilized man that
should be contrasted with that of savage man; and, when due regard is
paid to the all-important consideration which immediately follows, I
cannot feel that the contrast presents any difficulty to the theory of
human evolution by natural causation.
Lastly, the consideration just alluded to is, that civilized man enjoys
an advantage over savage man far in advance even of those which arise
from a settled state of society, incentives to intellectual training,
and so on. This inestimable advantage consists in the art of writing,
_and the consequent transmission of the effects of culture from
generation to generation_. Quite apart from any question as to the
hereditary transmission of acquired characters, we have in this
_intellectual_ transmission of acquired _experience_ a means of
accumulative cultivation quite beyond our powers to estimate. For,
unlike all other cases where we recognize the great influence of
individual use or practice in augmenting congenital "faculties" (such as
in the athlete, pianist, &c.), in this case the effects of special
cultivation do not end with the individual life, but are carried on and
on through successive generations _ad infinitum_. Hence, a civilized man
inherits mentally, if not physically, the effects of culture for ages
past, and this in whatever direction he may choose to profit therefrom.
Moreover--and I deem this an immensely important addition--in this
unique department of purely intellectual transmission, a kind of
non-physical natural selection is perpetually engaged in producing the
best results. For here a struggle for existence is constantly taking
place among "ideas," "methods," and so forth, in what may be termed a
psychological environment. The less fit are superseded by the more fit,
and this not only in the mind of the individual, but, through language
and literature, still more in the mind of the race. "A Newton, a La
Place, a Gauss, or a Cayley," would all alike have been impossible, but
for a previously prolonged course of mental evolution due to the
selection principle operating in the region of mathematics, by means of
continuous survivals of the best products in successive generations.
And, of course, the same remark applies to art in all its branches[22].
[22] In Prof. Lloyd Morgan's _Animal Life and Intelligence_ there is
an admirable discussion on this subject, which has been
published since the above was written. The same has to be said
of Weismann's Essay on Music, where much that I have here said
is anticipated. With the views and arguments which Mr. Mivart
has forcibly set forth I have already dealt to the best of my
ability in a work on _Mental Evolution in Man_.
Quitting then the last, and in my opinion the weakest chapter of
_Darwinism_, the most important points presented by other portions of
this work are--to quote its author's own enumeration of them--an
attempted "proof that all specific characters are (or once have been)
either useful in themselves or correlated with useful characters": an
attempted "proof that natural selection can, in certain cases, increase
the sterility of crosses": an attempted "proof that the effects of use
and disuse, even if inherited, must be overpowered by natural
selection": an attempted proof that the facts of variation in nature are
in themselves sufficient to meet the difficulty which arises against the
theory of natural selection, as held by him, from the swamping effects
of free intercrossing: and, lastly, "a fuller discussion on the colour
relations of animals, with additional facts and arguments on the origin
of sexual differences of colour." As I intend to deal with all these
points hereafter, excepting the last, it will be sufficient in this
opening chapter to remark, that in as far as I disagree with Mr. Wallace
(and agree with Darwin), on the subject of "sexual differences of
colour," my reasons for doing so have been already sufficiently stated
in Part I. But there is much else in his treatment of this subject which
appears to me highly valuable, and therefore presenting an admirable
contribution to the literature of Darwinism. In particular, it appears
to me that the most important of his views in this connexion probably
represents the truth--namely, that, among the higher animals, more or
less conspicuous peculiarities of colour have often been acquired for
the purpose of enabling members of the same species quickly and
certainly to recognize one another. This theory was first published by
Mr. J. E. Todd, in 1888, and therefore but a short time before its
re-publication by Mr. Wallace. As his part in the matter has not been
sufficiently recognized, I should like to conclude this introductory
chapter by drawing prominent attention to the merits of Mr. Todd's
paper. For not only has it the merit of priority, but it deals with the
whole subject of "recognition colours"--or, as he calls them, "directive
colours"--in a more comprehensive manner than has been done by any of
his successors. In particular, he shows that the principle of
recognition-marking is not restricted to facilitating sexual
intercourse, but extends also to several other matters of importance in
the economy of animal life[23].
[23] _American Naturalist_, xxii. pp. 201-207.
* * * * *
Having thus briefly sketched the doctrines of the sundry Post-Darwinian
Schools from a general point of view, I shall endeavour throughout the
rest of this treatise to discuss in appropriate detail the questions
which have more specially come to the front in the post-Darwinian
period. It can scarcely be said that any one of these questions has
arisen altogether _de novo_ during this period; for glimmerings, more or
less conspicuous, of all are to be met with in the writings of Darwin
himself. Nevertheless it is no less true that only after his death have
they been lighted up to the full blaze of active discussion[24]. By far
the most important of them are those to which the rest of this treatise
will be confined. They are four in number, and it is noteworthy that
they are all intimately connected with the great question which Darwin
spent the best years of his life in contemplating, and which has
therefore, in one form or another, occupied the whole of the present
chapter--the question as to whether natural selection has been the sole
cause, or but the chief cause of modification.
[24] It is almost needless to say that besides the works mentioned
in this chapter, many others have been added to the literature
of Darwinism since Darwin's death. But as none of these profess
to contain much that is original, I have not thought it
necessary to consider any of them in this merely general review
of the period in question. In subsequent chapters, however,
allusions will be made to those among them which I deem of most
importance.
[Since this note was written and printed the following works
have been published to which it does not apply: _Animal Life
and Intelligence_, by Professor Lloyd Morgan; _The Colours of
Animals_, by Professor Poulton; and _Materials for the Study of
Variation_, by Mr. Bateson. All these works are of high value
and importance. Special reference should also be made to
Professor Weismann's Essays.]
The four questions above alluded to appertain respectively to Heredity,
Utility, Isolation, and Physiological Selection. Of these the first two
will form the subject-matter of the present volume, while the last two
will be dealt with in the final instalment of _Darwin, and after
Darwin_.
SECTION I
_HEREDITY_
CHAPTER II.
CHARACTERS AS HEREDITARY AND ACQUIRED (PRELIMINARY).
We will proceed to consider, throughout Section I of the present work,
the most important among those sundry questions which have come to the
front since the death of Darwin. For it was in the year after this event
that Weismann published the first of his numerous essays on the subject
of Heredity, and, unquestionably, it has been these essays which have
given such prominence to this subject during the last decade.
At the outset it is desirable to be clear upon certain points touching
the history of the subject; the limits within which our discussion is to
be confined; the relation in which the present essay stands to the one
that I published last year under the title _An Examination of
Weismannism_; and several other matters of a preliminary kind.
The problems presented by the phenomena of heredity are manifold; but
chief among them is the hitherto unanswered question as to the
transmission or non-transmission of acquired characters. This is the
question to which the present Section will be confined.
Although it is usually supposed that this question was first raised by
Weismann, such was not the case. Any attentive reader of the successive
editions of Darwin's works may perceive that at least from the year 1859
he had the question clearly before his mind; and that during the rest of
his life his opinion with regard to it underwent considerable
modifications--becoming more and more Lamarckian the longer that he
pondered it. But it was not till 1875 that the question was clearly
presented to the general public by the independent thought of Mr.
Galton, who was led to challenge the Lamarckian factors _in toto_ by way
of deduction from his theory of Stirp--the close resemblance of which to
Professor Weismann's theory of Germ-plasm has been shown in my
_Examination of Weismannism_. Lastly, I was myself led to doubt the
Lamarckian factors still further back in the seventies, by having found
a reason for questioning the main evidence which Mr. Darwin had adduced
in their favour. This doubt was greatly strengthened on reading, in the
following year, Mr. Galton's _Theory of Heredity_ just alluded to; and
thereupon I commenced a prolonged course of experiments upon the
subject, the general nature of which will be stated in future chapters.
Presumably many other persons must have entertained similar misgivings
touching the inheritance of acquired characters long before the
publication of Weismann's first essay upon the subject in 1883. The
question as to the inheritance of acquired characters was therefore
certainly not first raised by Weismann--although, of course, there is no
doubt that it was conceived by him independently, and that he had the
great merit of calling general attention to its existence and
importance. On the other hand, it cannot be said that he has succeeded
in doing very much towards its solution. It is for these reasons that
any attempt at dealing with Weismann's fundamental postulate--i.e. that
of the non-inheritance of acquired characters--was excluded from my
_Examination of Weismannism_. As there stated, he is justified in
assuming, for the purposes of his discussion, a negative answer to the
question of such inheritance; but evidently the question itself ought
not to be included within what we may properly understand by
"Weismannism." Weismannism, properly so called, is an elaborate system
of theories based on the fundamental postulate just mentioned--theories
having reference to the mechanism of heredity on the one hand, and to
the course of organic evolution on the other. Now it was the object of
the foregoing _Examination_ to deal with this system of theories _per
se_; and therefore we have here to take a new point of departure and to
consider separately the question of fact as to the inheritance or
non-inheritance of acquired characters. At first sight, no doubt, it
will appear that in adopting this method I am putting the cart before
the horse. For it may well appear that I ought first to have dealt with
the validity of Weismann's postulate, and not till then to have
considered the system of theories which he has raised upon it. But this
criticism is not likely to be urged by any one who is well acquainted
with the questions at issue. For, in the first place, it is notorious
that the question of fact is still open to question; and therefore it
ought to be considered separately, or apart from any theories which may
have been formed with regard to it. In the second place, our judgement
upon this question of fact must be largely influenced by the validity of
general reasonings, such as those put forward in the interests of rival
theories of heredity; and, as the theory of germ-plasm has been so
thoughtfully elaborated by Professor Weismann, I have sought to give it
the attention which it deserves as preliminary to our discussion of the
question of fact which now lies before us. Thirdly and lastly, even if
this question could be definitely answered by proving either that
acquired characters are inherited or that they are not, it would by no
means follow that Weismann's theory of heredity would be proved wholly
false in the one case, or wholly true in the other. That it need not be
wholly true, even were its fundamental postulate to be proved so, is
evident, because, although the fact might be taken to prove the theory
of Continuity, the theory of Germ-plasm is, as above stated, very much
more than this. That the theory of Germ-plasm need not be wholly false,
even if acquired characters should ever be proved heritable, a little
thought may easily show, because, in this event, the further question
would immediately arise as to the degrees and the comparative frequency
of such inheritance. For my own part, as stated in the _Examination_, I
have always been disposed to accept Mr. Galton's theory of Stirp in
preference to that of Germ-plasm on this very ground--i. e. that it does
not dogmatically exclude the possibility of an occasional inheritance of
acquired characters in faint though cumulative degrees. And whatever our
individual opinions may be touching the admissibility of such a _via
media_ between the theories of Pangenesis and Germ-plasm, at least we
may all agree on the desirability of fully considering the matter as a
preliminary to the discussion of the question of fact.
As it is not to be expected that even those who may have read my
previous essay can now carry all these points in their memories, I will
here re-state them in a somewhat fuller form.
The following diagram will serve to give a clearer view of the sundry
parts of Professor Weismann's system of theories, as well as of their
relations to one another.
[Illustration: Postulate as to the absolute non-inheritance of acquired
characters.]
Now, as just explained, the parts of this system which may be properly
and distinctively called "Weismannism" are those which go to form the
Y-like structure of deductions from the fundamental postulate.
Therefore, it was the Y-like system of deductions which were dealt with
in the _Examination of Weismannism_, while it is only his basal
postulate which has to be dealt with in the following chapters.
So much, then, for the relations of Weismann's system of theories to one
another. It is, however, of even more importance that we should gain a
clear view of the relations between his theory of _heredity_ to those of
Darwin and of Galton, as preliminary to considering the fundamental
question of fact.
As we have already seen, the theory of germ-plasm is not only a theory
of heredity: it is also, and more distinctively, a theory of evolution,
&c. As a theory of heredity it is grounded on its author's fundamental
postulate--the _continuity_ of germ-plasm. But as a theory of evolution,
it requires for its support this additional postulate, that the
continuity of germ-plasm has been _absolute_ "since the first origin of
life." It is clear that this additional postulate is not needed for his
theory of heredity, but only for his additional theory of evolution, &c.
There have been one or two other theories of heredity, prior to this
one, which, like it, have been founded on the postulate of Continuity of
the substance of heredity; but it has not been needful for any of these
theories to postulate further that this substance has been _always_ thus
isolated, or even that it is now _invariably_ so. For even though the
isolation be frequently invaded by influences of body-changes on the
congenital characters of this substance, it does not follow that this
principle of Continuity may not still be true _in the main_, even
although it is supplemented in some degree by that of use-inheritance.
Indeed, so far as the phenomena of heredity are concerned, it is
conceivable that all congenital characters were originally acquired,
and afterwards became congenital on account of their long inheritance. I
do not myself advocate this view as biologically probable, but merely
state it as logically possible, and in order to show that, so far as the
phenomena of heredity are concerned, there appears to be no reason for
Weismann's deduction that the principle of Continuity, if true at all,
must be _absolute_. And it would further appear, the only reason why he
makes this deduction (stem of the Y) is in order to provide a foundation
for his further theories of evolution, &c. (arms of the Y). It is indeed
necessary for these further theories that body-changes should never
exercise any hereditary influence on the hereditary endowments of
germ-plasm, and therefore it is that he posits the substance of heredity
as, not only continuous, but uninterruptably so "since the first origin
of life."
Now, this may be made more clear by briefly comparing Weismann's theory
with those of Darwin and of Galton. Weismann's theory of heredity, then,
agrees with its predecessors which we are considering in all the
following respects. The substance of heredity is particulate; is mainly
lodged in highly specialized cells; is nevertheless also distributed
throughout the general cellular tissues, where it is concerned in all
processes of regeneration, repair, and a-sexual reproduction; presents
an enormously complex structure, in that every constituent part of a
potentially future organism is represented in a fertilized ovum by
corresponding particles; is everywhere capable of virtually unlimited
multiplication, without ever losing its hereditary endowments; is often
capable of carrying these endowments in a dormant state through a long
series of generations until at last they reappear in what we recognize
as recursions. Thus far all three theories are in agreement. In fact,
the only matter of any great importance wherein they disagree has
reference to the doctrine of Continuity[25]. For while Darwin's theory
supposes the substance of heredity to be mainly formed anew in each
ontogeny, and therefore that the continuity of this substance is for the
most part interrupted in every generation[26], Weismann's theory
supposes this substance to be formed only during the phylogeny of each
species, and therefore to have been absolutely uninterrupted since the
first origin of life.
[25] Originally, Weismann's further assumption as to the perpetual
stability of germ-plasm, "since the first origin of sexual
reproduction," was another very important point of difference,
but this has now been withdrawn.
[26] I say "_mainly_ formed anew," and "_for the most part_
interrupted," because even Darwin's theory does not, as is
generally supposed, exclude the doctrine of Continuity _in
toto_.
But now, Galton's theory of heredity stands much nearer to Weismann's in
this matter of Continuity; for it is, as he says, a theory of "modified
pangenesis," and the modification consists in allowing very much more
for the principle of Continuity than is allowed by Darwin's theory; in
fact he expresses himself as quite willing to adopt (on adequate grounds
being shown) the doctrine of Continuity as absolute, and therefore
propounded, as logically possible, the identical theory which was
afterwards and independently announced by Weismann. Or, to quote his own
words--
"We might almost reserve our belief that the structural [i. e.
somatic] cells can react on the sexual elements at all, and we may
be confident that at most they do so in a very faint degree; in
other words, that acquired modifications are barely, if at all,
_inherited_, in the correct sense of that word[27]."
[27] _Theory of Heredity_ (Journ. Anthrop. Inst. 1875, p. 346).
So far Mr. Galton; but for Weismann's further theory of evolution, &c.,
it is necessary to postulate the additional doctrine in question; and it
makes a literally immeasurable difference to any theory of evolution
whether or not we entertain this additional postulate. For no matter how
faintly or how fitfully the substance of heredity may be modified by
somatic tissues, the Lamarckian principles are hypothetically allowed
some degree of play. And although this is a lower degree than Darwin
supposed, their influence in determining the course of organic evolution
may still have been enormous; seeing that their action in any degree
must always have been _directive_ of variation on the one hand, and
_cumulative_ on the other.
Thus, by merely laying this theory side by side with Weismann's we can
perceive at a glance how a _pure_ theory of _heredity_ admits of being
based on the postulate of Continuity alone, without cumbering itself by
any further postulate as to this Continuity being _absolute_. And this,
in my opinion is the truly scientific attitude of mind for us to adopt
as preliminary to the following investigation. For the whole
investigation will be concerned--and concerned only--with this question
of Continuity as absolute, or as admitting of degrees. There is, without
any question, abundant evidence to prove that the substance of heredity
is at least partly continuous (Gemmules). It may be that there is also
abundant evidence to prove this substance much more _largely_
continuous than Darwin supposed (Stirp); but be this as it may, it is
certain that any such question as to the _degree_ of continuity differs,
_toto caelo_, from that as to whether there can ever be any continuity
at all.
How, then, we may well ask, is it that so able a naturalist and so clear
a thinker as Weismann can have so far departed from the inductive
methods as to have not merely propounded the question touching
Continuity and its degrees, or even of Continuity as absolute; but to
have straightway assumed the latter possibility as a basis on which to
run a system of branching and ever-changing speculations concerning
evolution, variation, the ultimate structure of living material, the
intimate mechanism of heredity, or, in short, such a system of deductive
conjectures as has never been approached in the history of science? The
answer to this question is surely not far to seek. Must it not be the
answer already given? Must it not have been for the sake of rearing this
enormous structure of speculation that Weismann has adopted the
assumption of Continuity as absolute? As we have just seen, Galton had
well shown how a theory of heredity could be founded on the general
doctrine of Continuity, without anywhere departing from the inductive
methods--even while fully recognizing the possibility of such continuity
as absolute. But Galton's theory was a "_Theory of Heredity_," and
nothing more. Therefore, while clearly perceiving that the Continuity in
question _may_ be absolute, he saw no reason, either in fact or in
theory, for concluding that it _must_ be. On the contrary, he saw that
this question is, for the present, necessarily unripe for profitable
discussion--and, _a fortiori_, for the shedding of clouds of seed in all
the directions of "Weismannism."
Hence, what I desire to be borne in mind throughout the following
discussion is, that it will have exclusive reference to the question of
fact already stated, without regard to any superjacent theories; and,
still more, that there is a vast distinction between any question
touching the degrees in which acquired characters are transmitted to
progeny, and the question as to whether they are ever transmitted in any
degree at all. Now, the latter question, being of much greater
importance than the former, is the one which will mainly occupy our
attention throughout the rest of this Section.
We have already seen that before the subject was taken up by Weismann
the difference between acquired and congenital characters in respect to
transmissibility was generally taken to be one of degree; not one of
kind. It was usually supposed that acquired characters, although not so
fully and not so certainly inherited as congenital characters,
nevertheless were inherited in some lesser degree; so that if the same
acquired character continued to be successively acquired in a number of
sequent generations, what was at first only a slight tendency to be
inherited would become by summation a more and more pronounced tendency,
till eventually the acquired character might become as strongly
inherited as a congenital one. Or, more precisely, it was supposed that
an acquired character, in virtue of such a summation of hereditary
influence, would in time become congenital. Now, if this supposition be
true, it is evident that more or less assistance must be lent to
natural selection in its work of evolving adaptive modifications[28].
And inasmuch as we know to what a wonderful extent adaptive
modifications are secured during individual life-times--by the direct
action of the environment on the one hand, and by increased or
diminished use of special organs and mental faculties on the other--it
becomes obvious of what importance even a small measure of
transmissibility on their part would be in furnishing to natural
selection ready-made variations in required directions, as distinguished
from promiscuous variations in all directions. Contrariwise, if
functionally-produced adaptations and adaptations produced by the direct
action of the environment are never transmitted in any degree, not only
would there be an incalculable waste, so to speak, of adaptive
modifications--these being all laboriously and often most delicately
built up during life-times of individuals only to be thrown down again
as regards the interest of species--but so large an additional burden
would be thrown upon the shoulders of natural selection that it becomes
difficult to conceive how even this gigantic principle could sustain it,
as I shall endeavour to show more fully in future chapters. On the other
hand, however, Weismann and his followers not only feel no difficulty in
throwing overboard all this ready-made machinery for turning out
adaptive modifications when and as required; but they even represent
that by so doing they are following the logical maxim, _Entia non sunt
multiplicanda praeter necessitatem_--which means, in its relation to
causality, that we must not needlessly multiply hypothetical principles
to explain given results. But when appeal is here made to this logical
principle--the so-called Law of Parsimony--two things are forgotten.
[28] Mr. Platt Ball has, indeed, argued that "use-inheritance would
often be an evil," since, for example, "the condyle of the
human jaw would become larger than the body of the jaw, because
as the fulcrum of the lever it receives more pressure"; and
similarly as regards many other hypothetical cases which he
mentions. (_The Effects of Use and Disuse_, pp. 128-9 _et
seq._) But it is evident that this argument proves too much.
For if the effects of use and disuse as transmitted to progeny
would be an evil, it could only be because these effects as
they occur in the parents are an evil--and this they most
certainly are not, being, on the contrary and as a general
rule, of a high order of adaptive value. Moreover, in the race,
there is a superadded agency always at work, which must
effectually prevent any undue accumulation of these
effects--namely, natural selection, which every Darwinist
accepts as a controlling principle of all or any other
principles of change. Therefore, if, as first produced in the
life-time of individuals, the effects of use and disuse are not
injurious, much less can they become so if transmitted through
the life-time of species. Again, Mr. Wallace argues that, even
supposing use-inheritance to occur, its adapting work in the
individual can never extend to the race, seeing that the
natural selection of fortuitous variations in the directions
required must always produce the adaptations _more quickly_
than would be possible by use-inheritance. This argument, being
one of more weight, will be dealt with in a future chapter.
In the first place, it is forgotten that the very question in debate is
whether causes of the Lamarckian order _are_ unnecessary to explain all
the phenomena of organic nature. Of course if it could be proved that
the theory of natural selection alone is competent to explain all these
phenomena, appeal to the logical principle in question would be
justifiable. But this is precisely the point which the followers of
Darwin refuse to accept; and so long as it remains the very point at
issue, it is a mere begging the question to represent that a class of
causes which have hitherto been regarded as necessary are, in fact,
unnecessary. Or, in other words, when Darwin himself so decidedly held
that these causes are necessary as supplements to natural selection, the
burden of proof is quite as much on the side of Weismann and his
followers to show that Darwin's opinion was wrong, as it is on the side
of Darwin's followers to show that it was right. Yet, notwithstanding
the elaborate structure of theory which Weismann has raised, there is
nowhere one single fact or one single consideration of much importance
to the question in debate which was not perfectly well known to Darwin.
Therefore I say that all this challenging of Darwinists to justify their
"Lamarckian assumptions" really amounts to nothing more than a pitting
of opinion against opinion, where there is at least as much call for
justification on the one side as on the other.
Again, when these challenges are thrown down by Weismann and his
followers, it appears to be forgotten that the conditions of their own
theory are such as to render acceptance of the gauge a matter of great
difficulty. The case is very much like that of a doughty knight pitching
his glove into the sea, and then defying any antagonist to take it up.
That this is the case a very little explanation will suffice to show.
The question to be settled is whether acquired characters are ever
transmitted by heredity. Now suppose, for the sake of argument, that
acquired characters are transmitted by heredity--though not so fully and
not so certainly as congenital characters--how is this fact to be proved
to the satisfaction of Weismann and his followers? First of all they
answer,--Assuredly by adducing experimental proof of the inheritance of
injuries, or mutilations. But in making this answer they appear to
forget that Darwin has already shown its inefficiency. That the
self-styled Neo-Lamarckians have been much more unguarded in this
respect, I fully admit; but it is obviously unfair to identify Darwin's
views with those of a small section of evolutionists, who are really as
much opposed to Darwin's teaching on one side as is the school of
Weismann on the other. Yet, on reading the essays of Weismann
himself--and still more those of his followers--one would almost be led
to gather that it is claimed by him to have enunciated the distinction
between congenital and acquired characters in respect of
transmissibility; and therefore also to have first raised the objection
which lies against the theory of Pangenesis in respect of the
non-transmissibility of mutilations. In point of fact, however, Darwin
is as clear and decided on these points as Weismann. And his answer to
the obvious difficulty touching the non-transmissibility of mutilations
is, to quote his own words, "the long-continued inheritance of a part
which has been removed during many generations is no real anomaly, for
gemmules formerly derived from the part are multiplied and transmitted
from generation to generation[29]." Therefore, so far as Darwin's theory
is concerned, the challenge to produce evidence of the transmission of
injuries is irrelevant: it is no more a part of Darwin's theory than it
is of Weismann's to maintain that injuries _are_ transmitted.
[29] _Variation under Domestication_, ii. 392.
There is, however, one point in this connexion to which allusion must
here be made. Although Darwin did not believe in the transmissibility
of mutilations when these consist merely in the amputation of parts of
an organism, he did believe in a probable tendency to transmission when
removal of the part is followed by gangrene. For, as he says, in that
case, all the gemmules of the mutilated or amputated part, as they are
gradually attracted to that part (in accordance with the law of affinity
which the theory assumes), will be successively destroyed by the morbid
process. Now it is of importance to note that Darwin made this exception
to the general rule of the non-transmissibility of mutilations, not
because his theory of pangenesis required it, but because there appeared
to be certain very definite observations and experiments--which will be
mentioned later on--proving that when mutilations are followed by
gangrene they are apt to be inherited: his object, therefore, was to
reconcile these alleged facts with his theory, quite as much as to
sustain his theory by such facts.
So much, then, for the challenge to produce direct evidence of the
transmissibility of acquired characters, so far as mutilations are
concerned: believers in Darwin's theory, as distinguished from
Weismann's, are under no obligation to take up such a challenge. But the
challenge does not end here. Show us, say the school of Weismann, a
single instance where an acquired character _of any kind_ (be it a
mutilation or otherwise) has been inherited: this is all that we
require: this is all that we wait for: and surely, unless it be
acknowledged that the Lamarckian doctrine reposes on mere assumption, at
least one such case ought to be forthcoming. Well, nothing can sound
more reasonable than this in the first instance; but as soon as we
begin to cast about for cases which will satisfy the Neo-Darwinians, we
find that the structure of their theory is such as to preclude, in
almost every conceivable instance, the possibility of meeting their
demand. For their theory begins by assuming that natural selection is
the one and only cause of organic evolution. Consequently, what their
demand amounts to is throwing upon the other side the burden of
disproving this assumption--or, in other words, of proving the negative
that in any given case of transmitted adaptation natural selection has
_not_ been the sole agent at work. Now, it must obviously be in almost
all cases impossible to prove this negative among species in a state of
nature. For, even supposing that among such species Lamarckian
principles have had a large share in the formation of hereditary and
adaptive characters, how would Weismann himself propose that we should
set about the proof of such a fact, where the proof demanded by his
assumption is, that the _abstract possibility_ of natural selection
having had anything to do with the matter must be excluded? Obviously
this is impossible in the case of inherited characters which are also
_adaptive_ characters. How then does it fare with the case of inherited
characters which are not also adaptive? Merely that this case is met by
another and sequent assumption, which constitutes an integral part of
the Neo-Darwinian creed--namely, that in nature there _can be no such
characters_. Seeing that natural selection is taken to be the only
possible cause of change in species, it follows that all changes
occurring in species must necessarily be adaptive, whether or not we are
able to perceive the adaptations. In this way apparently useless
characters, as well as obviously useful ones, are ruled out of the
question: that is to say, _all_ hereditary characters of species in a
state of nature are _assumed_ to be due to natural selection, and then
it is demanded that the validity of this assumption should be disproved
by anybody who doubts it. Yet Weismann himself would be unable to
suggest any conceivable method by which it can be disproved among
species in a state of nature--and this even supposing that the
assumption is entirely false[30].
[30] In subsequent chapters, especially devoted to the question
(i.e. Section II), the validity of this assumption will be
considered on its own merits.
Consequently, the only way in which these speciously-sounding challenges
can be adequately met is by removing some individuals of a species from
a state of nature, and so from all known influences of natural
selection; then, while carefully avoiding artificial selection, causing
these individuals and their progeny through many generations unduly to
exercise some parts of their bodies, or unduly to fail in the exercise
of others. But, clearly, such an experiment is one that must take years
to perform, and therefore it is now too early in the day to reproach the
followers of Darwin with not having met the challenges which are thrown
down by the followers of Weismann[31].
[31] I say "the followers of Weismann," because Weismann himself,
with his clear perception of the requirements of experimental
research, expressly states the above considerations, with the
conclusions to which they lead. Nevertheless, he is not
consistent in his utterances upon this matter; for he
frequently expresses himself to the effect, "that the _onus
probandi_ rests with my opponents, and therefore they ought to
bring forward actual proofs" (_Essays_, i. p. 390). But, as
above shown, the _onus_ rests as much with him as with his
opponents; while, even if his opponents are right, he elsewhere
recognizes that they can bring "actual proofs" of the fact only
as a result of experiments which must take many years to
perform.
Probably enough has now been said to show that the Neo-Darwinian
assumption precludes the possibility of its own disproof from any of the
facts of nature (as distinguished from domestication)--and this even
supposing that the assumption be false. On the other hand, of course, it
equally precludes the possibility of its own proof; and therefore it is
as idle in Darwinists to challenge Weismann for proof of his negative
(i. e. that acquired characters are not transmitted), as it is in
Weismann to challenge Darwinists for proof of the opposite negative (i.
e. that all seeming cases of such transmission are not due to natural
selection). This dead-lock arises from the fact that in nature it is
beyond the power of the followers of Darwin to exclude the abstract
possibility of natural selection in any given case, while it is equally
beyond the power of the followers of Weismann to exclude the abstract
possibility of Lamarckian principles. Therefore at present the question
must remain for the most part a matter of opinion, based upon general
reasoning as distinguished from special facts or crucial experiments.
The evidence available on either side is presumptive, not
demonstrative[32]. But it is to be hoped that in the future, when time
shall have been allowed for the performance of definite experiments on a
number of generations of domesticated plants or animals, intentionally
shielded from the influences of natural selection while exposed to those
of the Lamarckian principles, results will be gained which will finally
settle the question one way or the other.
[32] Note A.
Meanwhile, however, we must be content with the evidence as it stands;
and this will lead us to the second division of our subject. That is to
say, having now dealt with the antecedent, or merely logical, state of
the question, we have next to consider what actual, or biological,
evidence there is at present available on either side of it. Thus far,
neither side in the debate has any advantage over the other. On grounds
of general reasoning alone they both have to rely on more or less
dogmatic assumptions. For it is equally an unreasoned statement of
opinion whether we allege that all the phenomena of organic evolution
can be, or can not be, explained by the theory of natural selection
alone. We are at present much too ignorant touching the causes of
organic evolution to indulge in dogmatism of this kind; and if the
question is to be referred for its answer to authority, it would appear
that, both in respect of number and weight, opinions on the side of
having provisionally to retain the Lamarckian factors are more
authoritative than those _per contra_[33].
[33] For a fair and careful statement of the present balance of
authoritative opinion upon the question, see H. F. Osborn,
_American Naturalist_, 1892, pp. 537-67.
* * * * *
Turning then to the question of fact, with which the following chapters
are concerned, I will conclude this preliminary one with a few words on
the method of discussion to be adopted.
First I will give the evidence in favour of Lamarckianism; this will
occupy the next two chapters. Then, in Chapter V, I will similarly give
the evidence _per contra_, or in favour of Continuity as absolute.
Lastly, I will sum up the evidence on both sides, and give my own
judgement on the whole case. But on whichever side I am thus acting as
special pleader for the time being, I will adduce only such arguments as
seem to me valid--excluding alike from both the many irrelevant or
otherwise invalid reasonings which have been but too abundantly
published. Moreover, I think it will be convenient to consider all that
has been said--or may be said--in the way of criticism to each argument
by the opposite side while such argument is under discussion--i. e. not
to wait till all the special pleading on one side shall have been
exhausted before considering the exceptions which have been (or admit of
being) taken to the arguments adduced, but to deal with such exceptions
at the time when each of these arguments shall have been severally
stated. Again, and lastly, I will arrange the evidence in each case--i.
e. on both sides--under three headings, viz. (A) Indirect, (B) Direct,
and (C) Experimental[34].
[34] [The above paragraph is allowed to remain exactly as Mr.
Romanes left it. Chapters V and VI were however not completed.
_See_ note appended to Preface. C. Ll. M.]
CHAPTER III.
CHARACTERS AS HEREDITARY AND ACQUIRED
(_continued_).
(A.)
_Indirect Evidence in favour of the Inheritance of Acquired Characters._
Starting with the evidence in favour of the so-called Lamarckian
factors, we have to begin with the Indirect--and this without any
special reference to the theories, either of Weismann or of others.
It has already been shown, while setting forth in the preceding chapter
the antecedent standing of the issue, that in this respect the _prima
facie_ presumption is wholly on the side of the transmission, in greater
degree or less, of acquired characters. Even Weismann allows that all
"_appearances_" point in this direction, while there is no inductive
evidence of the action of natural selection in any one case, either as
regards germs or somas, and therefore, _a fortiori_, of the
"all-sufficiency" of this cause[35]. It is true that in some of his
earlier essays he has argued that there is no small weight of _prima
facie_ evidence in favour of his own views as to the non-inheritance of
acquired characters. This, however, will have to be considered in its
proper place further on. Meanwhile I shall say merely in general terms
that it arises almost entirely from a confusion of the doctrine of
Continuity as absolute with that of Continuity as partial, and
therefore, as admitting of degrees in different cases--which, as already
explained, are doctrines wide as the poles asunder. But, leaving aside
for the present such _prima facie_ evidence as Weismann has adduced on
his side of the issue, I may quote him as a hostile witness to the
weight of this kind of evidence _per contra_, in so far as it has
already been presented in the foregoing chapter. Indeed, Weismann is
much too logical a thinker not to perceive the cogency of the
"appearances" which lie against his view of Continuity as
absolute--although he has not been sufficiently careful in
distinguishing between such Continuity and that which admits of degrees.
[35] See, especially, his excellent remarks on this point, _Contemp.
Rev._ Sept. 1893.
We may take it, then, as agreed on all hands that whatever weight merely
_prima facie_ evidence may in this matter be entitled to, is on the side
of what I have termed moderated Lamarckianism: first sight "appearances"
are against the Neo-Darwinian doctrine of the absolute non-inheritance
of acquired characters.
* * * * *
Let us now turn to another and much more important line of indirect
evidence in favour of moderated Lamarckianism.
The difficulty of _excluding the possibility_ of natural selection
having been at work in the case of wild plants and animals has already
been noticed. Therefore we may now appreciate the importance of all
facts or arguments which _attenuate the probability_ of natural
selection having been at work. This may be done by searching for cases
in nature where a congenital structure, although unquestionably
adaptive, nevertheless presents so small an amount of adaptation, that
we can scarcely suppose it to have been arrived at by natural selection
in the struggle for existence, as distinguished from the inheritance of
functionally-produced modifications. For if functionally-produced
modifications are ever transmitted at all, there is no limit to the
minuteness of adaptive values which may thus become congenital; whereas,
in order that any adaptive structure or instinct should be seized upon
and accumulated by natural selection, it must from the very first have
had an adaptive value sufficiently great to have constituted its
presence a matter of life and death in the struggle for existence. Such
structures or instincts must not only have always presented some measure
of adaptive value, but this must always have been sufficiently great to
reach what I have elsewhere called a selection-value. Hence, if we meet
with cases in nature where adaptive structures or instincts present so
low a degree of adaptive value that it is difficult to conceive how they
could ever have exercised any appreciable influence in the battle for
life, such cases may fairly be adduced in favour of the Lamarckian
theory. For example, the Neo-Lamarckian school of the United States is
chiefly composed of palaeontologists; and the reason of this seems to be
that the study of fossil forms--or of species in process of
formation--reveals so many instances of adaptations which in their
nascent condition present such exceedingly minute degrees of adaptive
value, that it seems unreasonable to attribute their development to a
survival of the fittest in the complex struggle for existence. But as
this argument is in my opinion of greatest force when it is applied to
certain facts of physiology with which I am about to deal, I will not
occupy space by considering any of the numberless cases to which the
Neo-Lamarckians apply it within the region of palaeontology[36].
[36] There is now an extensive literature within this region. The
principal writers are Cope, Scott and Osborn. Unfortunately,
however, the facts adduced are not crucial as test-cases
between the rival theories--nearly all of them, in fact, being
equally susceptible of explanation by either.
Turning then to inherited actions, it is here that we might antecedently
expect to find our best evidence of the Lamarckian principles, if these
principles have really had any share in the process of adaptive
evolution. For we know that in the life-time of individuals it is
action, and the cessation of action, which produce nearly all the
phenomena of acquired adaptation--use and disuse in animals being merely
other names for action and the cessation of action. Again, we know that
it is where neuro-muscular machinery is concerned that we meet with the
most conclusive evidence of the remarkable extent to which action is
capable of co-ordinating structures for the ready performance of
particular functions; so that even during the years of childhood
"practice makes perfect" to the extent of organizing neuro-muscular
adjustments, so elaborate and complete as to be indistinguishable from
those which in natural species we recognized as reflex actions on the
one hand, and instinctive actions on the other. Hence, if there be any
such thing as "use-inheritance" at all, it is in the domain of reflex
actions and instinctive actions that we may expect to find our best
evidence of the fact. Therefore I will restrict the present line of
evidence--(A)--to these two classes of phenomena, as together yielding
the best evidence obtainable within this line of argument.
* * * * *
The evidence in favour of the Lamarckian factors which may be derived
from the phenomena of reflex action has never, I believe, been pointed
out before; but it appears to me of a more cogent nature than perhaps
any other. In order to do it justice, I will begin by re-stating an
argument in favour of these factors which has already been adduced by
previous writers, and discussed by myself in published correspondence
with several leaders of the ultra-Darwinian school.
Long ago Professor Broca and Mr. Herbert Spencer pointed to the facts of
co-adaptation, or co-ordination within the limits of the same organism,
as presenting good evidence of Lamarckian principles, working in
association with natural selection. Thus, taking one of Lamarck's own
illustrations, Mr. Spencer argued that there must be numberless
changes--extending to all the organs, and even to all the tissues, of
the animal--which in the course of many generations have conspired to
convert an antelope into a giraffe. Now the point is, that throughout
the entire history of these changes their utility must always have been
dependent on their association. It would be useless that an incipient
giraffe should present the peculiar form of the hind-quarters which we
now perceive, unless at the same time it presented the correspondingly
peculiar form of the fore-quarters; and as each of these great
modifications entails innumerable subordinate modifications throughout
both halves of the creature concerned, the chances must have been
infinitely great against the required association of so many changes
happening to have arisen congenitally in the same individuals by way of
merely fortuitous variation. Yet, if we exclude the Lamarckian
interpretation, which gives an intelligible _cause_ of co-ordination, we
are required to suppose that such a happy concurrence of innumerable
independent variations must have occurred by mere accident--and this on
innumerable different occasions in the bodies of as many successive
ancestors of the existing species. For at each successive stage of the
improvement natural selection (if working alone) must have needed all,
or at any rate most, of the co-ordinated parts to occur in the same
individual organisms[37].
[37] For another and better illustration more recently published by
Mr. Spencer, see _The Inadequacy of Natural Selection_, p. 22.
In alluding to what I have already published upon the difficulty which
thus appears to be presented to his theory, Weismann says, "At no
distant time I hope to be able to consider this objection, and to show
that the apparent support given to the old idea [i. e. of the
transmission of functionally-produced modifications] is really insecure,
and breaks down as soon as it is critically examined[38]."
[38] _Essays on Heredity_, vol. i. p. 389.
[For further treatment of the subject under discussion _see_
Weismann, _The All-sufficiency of Natural Selection_ (Contemp.
Rev. Sept. and Oct. 1893), and _The Effect of External
Influences upon Development_. "Romanes Lecture" 1894, and
Spencer, _Weismannism once more_ (Cont. Rev. Oct. 1894). C. Ll.
M.]
So much for what Weismann has said touching this matter. But the matter
has also been dealt with both by Darwin and by Wallace. Darwin very
properly distinguishes between the fallacy that "with animals such as
the giraffe, of which the whole structure is admirably co-ordinated for
certain purposes, it has been supposed that all the parts must have been
simultaneously modified[39]," and the sound argument that the
co-ordination itself cannot have been due to natural selection alone.
This important distinction may be rendered more clear as follows.
[39] _Variation_, &c., vol. ii. p. 206.
The facts of artificial selection prove that immense modifications of
structure may be caused by a cumulative blending in the same individuals
of characters which were originally distributed among different
individuals. Now, in the parallel case of natural selection the
characters thus blended will usually--if not invariably--be of an
adaptive kind; and their eventual blending together in the same
individuals will be due to free intercrossing of the most fit. But this
_blending of adaptations_ is quite a different matter from the
_occurrence of co-ordination_. For it belongs to the essence of
co-ordination that each of the co-ordinated parts should be destitute of
adaptive value _per se_: the adaptation only begins to arise if all the
parts in question occur associated together in the same individuals
_from the very first_. In this case it is obvious that the analogy of
artificial selection can be of no avail in explaining the facts, since
the difficulty presented has nothing to do with the blending in single
individuals of adaptations previously distributed among different
individuals; it has to do with the simultaneous appearance in single
individuals of a co-adaptation of parts, none of which could ever have
been of any adaptive value had it been previously distributed among
different individuals. Consequently, where Darwin comes to consider this
particular case (or the case of co-adaptation as distinguished from the
blending of adaptations), he freely invokes the aid of the Lamarckian
principles[40].
[40] E. g. _Origin of Species_, p. 178.
Wallace, on the other hand, refuses to do this, and says that "the best
answer to the difficulty" of supposing natural selection to have been
the only cause of co-adaptation may be "found in the fact that the very
thing said to be impossible by variation and natural selection, has been
again and again affected by variation and artificial selection[41]."
This analogy (which Darwin had already and very properly adduced with
regard to the _blending of adaptations_) he enforces by special
illustrations; but he does not appear to perceive that it misses the
whole and only point of the "difficulty" against which it is brought.
For the case which his analogy sustains is not that which Darwin,
Spencer, Broca and others, mean by _co-adaptation_: it is the case of a
blending of _adaptations_. It is not the case where adaptation is _first
initiated in spite of intercrossing_, by a fortuitous concurrence of
variations each in itself being without adaptive value: it is the case
where adaptation is _afterwards increased by means of intercrossing_,
through the blending of variations each of which has always been in
itself of adaptive value.
[41] _Darwinism_, p. 418.
From this I hope it will be apparent that the only way in which the
"difficulty" from co-adaptation can be logically met by the
ultra-Darwinian school, is by denying that the phenomenon of
co-adaptation (as distinguished from the blending of adaptations) is
ever to be really met with in organic nature. It may be argued that in
all cases where co-adaptation _appears_ to occur, closer examination
will show that the facts are really due to a blending of adaptations.
The characters A + B + C + D, which are now found united in the same
organism, and, as thus united, all conspiring to a common end, may
originally have been distributed among different organisms, where they
_severally_ subserved some other ends--or possibly the same end, though
in a less efficient manner. Obviously, however, in this case their
subsequent combination in the same organism would not be an instance of
co-adaptation, but merely of an advantageous blending together of
already existing adaptations. This argument, or rejoinder, has in point
of fact been adopted by Professor Meldola, he believes that all cases of
seeming co-adaptation are thus due to a mere blending of
adaptations[42]. Of course, if this position can be maintained, the
whole difficulty from co-adaptation would lapse. But even then it would
lapse on the ground of _fact_. It would not have been overturned, or in
any way affected, by Wallace's _argument_ from artificial selection.
For, in that event, no such argument would be required, and, if adduced,
would be irrelevant, since no one has ever alleged that there is any
difficulty in understanding the mere confluence of adaptations by
free-intercrossing of the best adapted.
[42] _Nature_, vol. xliii. pp. 410, 557; vol. xliv. pp. 7, 29. I say
"adopted," because I had objected to his quoting the analogy of
artificial selection, and stated, as above, that the only way
to meet Mr. Spencer's "difficulty" was to deny the fact of
co-adaptation as ever occurring in any case. It then appeared
that Professor Meldola agreed with me as to this. But I do not
yet understand why, if such were his view, he began by
endorsing Mr. Wallace's analogy from artificial selection--i.
e. confusing the case of co-adaptation with that of the
blending of adaptations. If any one denies the fact of
co-adaptation, he cannot assist his denial by arguing the
totally different fact that adaptations may be blended by free
intercrossing; for this latter fact has never been questioned,
and has nothing to do with the one which he engaged in
disputing.
Now, if we are agreed that the only question in debate is the question
of fact whether or not co-adaptation ever occurs in nature, it appears
to me that the best field for debating the question is furnished by the
phenomena of reflex action. I can well perceive that the instances
adduced by Broca and Spencer in support of their common argument--such
as the giraffe, the elk, &c.--are equivocal. But I think that many
instances which may be adduced of reflex action are much more to the
point. _For it belongs to the very nature of reflex action that it
cannot work unless all parts of the machinery concerned are already
present, and already co-ordinated, in the same organism._ It would be
useless, in so far as such action is concerned if the afferent and
efferent nerves, the nerve-centre, and the muscles organically grouped
together, were not all present from the very first in the same
individuals, and from the very first were not co-ordinated as a definite
piece of organic machinery.
With respect to reflex actions, therefore, it is desirable to begin by
pointing out how widely the adaptations which they involve differ from
those where no manufacture, so to speak, of special machinery is
required. Thus, it is easy to understand how natural selection alone is
capable of gradually accumulating congenital variations in the direction
of protective colouring; of mimicry; of general size, form, mutual
correlation of parts as connected with superior strength, fleetness,
agility, &c.; of greater or less development of particular parts, such
as legs, wings, tails, &c. For in all such cases the adaptation which is
in process of accumulation is from its very commencement and throughout
each of its subsequent stages, of _use_ in the struggle for existence.
And inasmuch as all the individuals of each successive generation vary
round the specific mean which characterized the preceding generation,
there will always be a sufficient number of individuals which present
congenital variations of the kind required for natural selection to
seize upon, without danger of their being swamped by free
intercrossing--as Mr. Wallace has very ably shown in his _Darwinism_.
But this law of averages can apply only to cases where single
structures--or a single group of correlated structures--are already
present, and already varying round a specific mean. The case is quite
different where a _co-ordination_ of structures is required for the
performance of a _previously non-existent_ reflex action. For some, at
least, of these structures must be _new_, as must also be the function
which all of them first conspire to perform. Therefore, neither the new
elements of structure, nor the new combination of structures, can have
been previously given as varying round a specific mean. On the contrary,
a very definite piece of machinery, consisting of many co-ordinated
parts, must somehow or other be originated in a high degree of working
efficiency, before it can be capable of answering its purpose in the
prompt performance of a particular action under particular circumstances
of stimulation. Lastly, such pieces of machinery are always of a highly
delicate character, and usually involve so immensely complex a
co-ordination of mutually dependent parts, that it is only a
physiologist who can fully appreciate the magnitude of the distinction
between "adaptations" of this kind, and "adaptations" of the kind which
arise through natural selection seizing upon congenital variations as
these oscillate round a specific mean.
Or the whole argument may be presented in another form, under three
different headings, thus:--
In the first place, it will be evident from what has just been said,
that such a piece of machinery as is concerned in even the simplest
reflex action cannot have occurred in any considerable number of
individuals of a species, _when it first began to be constructed_. On
the contrary, if its _origin_ were dependent on congenital variations
alone, the needful co-adaptation of parts which it requires can scarcely
have happened to occur in more than a very small percentage of
cases--even if it be held conceivable that by such means alone it should
ever have occurred at all. Hence, instead of preservation and subsequent
improvement having taken place _in consequence of_ free intercrossing
among all individuals of the species (as in the cases of protective
colouring, &c., where adaptation has no reference to any mechanical
co-adaptation of parts), they must have taken place _in spite of_ such
intercrossing.
In the second place, adaptations due to organic machineries of this kind
differ in another all-important respect from those due to a summation of
adaptive characters which are already present and already varying round
a specific mean. The latter depend for their summation upon the
fact--not merely, as just stated, that they are already present, already
varying round a specific mean, and therefore owe their progressive
evolution to free intercrossing, but also--_that they admit of very
different degrees of adaptation_. It is only because the degree of
adaptation in generation B is superior to that in generation A that
_gradual improvement_ in respect of adaptation is here possible. In the
case of protective resemblance, for example, a very imperfect and merely
accidental resemblance to a leaf, to another insect, &c., may at the
first start have conferred a sufficient degree of adaptive imitation to
count for something in the struggle for life; and, if so, the basis
would be given for a progressive building up by natural selection of
structures and colours in ever-advancing degrees of adaptive
resemblance. There is here no necessity to suppose--nor in point of fact
is it ever supposed, since the supposition would involve nothing short
of a miracle--that such extreme perfection in this respect as we now so
frequently admire has originated suddenly in a single generation, as a
collective variation of a congenital kind affecting simultaneously a
large proportional number of individuals. But in the case of a reflex
mechanism--which may involve even greater marvels of adaptive
adjustment, and _all_ the parts of which must occur in the same
_individuals_ to be of any use--it _is_ necessary to suppose some such
sudden and collective origin in some very high degree of efficiency, if
natural selection has been the only principle concerned in afterwards
perfecting the mechanism. For it is self-evident that a reflex action,
from its very nature, cannot admit of any great differences in its
degrees of adaptation: if it is to work at all, so as to count for
anything in the struggle for life, it must already be given in a state
of working efficiency. So that, unless we invoke either the doctrine of
"prophetic types" or the theory of sudden creations, I confess I do not
see how we are to explain either the origin, or the development, of a
reflex mechanism by means of natural selection alone.
Lastly, in the third place, _even when reflex mechanisms have been fully
formed_, it is often beyond the power of sober credence to believe that
they now are, or ever can have been, of selective value in the struggle
for existence, as I will show further on. And such cases go to fortify
the preceding argument. For if not conceivably of selective value even
when completely evolved, much less can they conceivably have been so
through all the stages of their complex evolution back to their very
origin. Therefore, supposing for the present that there are such cases
of reflex action in nature, neither their origin nor their development
can conceivably have been due to natural selection alone. The Lamarckian
factors, however, have no reference to degrees of adaptation, any more
than they have to degrees of complexity. No question of value, as
selective or otherwise, can obtain in their case: neither in their case
does any difficulty obtain as regards the co-adaptation of severally
useless parts.
Now, if all these distinctions between the Darwinian and Lamarckian
principles are valid--and I cannot see any possibility of doubt upon
this point--strong evidence in favour of the latter would be furnished
by cases (if any occur) where structures, actions, instincts, &c.,
although of some adaptive value, are nevertheless plainly not of
selective value. According to the ultra-Darwinian theory, no such cases
ought ever to occur: according to the theory of Darwin himself, they
ought frequently to occur. Therefore a good test, or criterion, as
between these different theories of organic evolution is furnished by
putting the simple question of fact--Can we, or can we not, show that
there are cases of adaptation where the degree of adaptation is so small
as to be incompatible with the supposition of its presenting a selective
value? And if we put the wider question--Are there any cases where the
co-adaptation of severally useless parts has been brought about, when
even the resulting whole does not present a selective value?--then, of
course, we impose a still more rigid test.
Well, notwithstanding the difficulty of proving such a negative as the
absence of natural selection where adaptive development is concerned, I
believe that there are cases which conform to both these tests
simultaneously; and, moreover, that they are to be found in most
abundance where the theory of use-inheritance would most expect them to
occur--namely, in the province of reflex action. For the very essence of
this theory is the doctrine, that constantly associated use of the same
parts for the performance of the same action will progressively organize
those parts into a reflex mechanism--no matter how high a degree of
co-adaptation may thus be reached on the one hand, or how low a degree
of utilitarian value on the other.
Having now stated the general or abstract principles which I regard as
constituting a defence of the Lamarckian factors, so far as this admits
of being raised on grounds of physiology, we will now consider a few
concrete cases by way of illustration. It is needless to multiply such
cases for the mere purpose of illustration. For, on reading those here
given, every physiologist will at once perceive that they might be added
to indefinitely. The point to observe is, the relation in which these
samples of reflex action stand to the general principles in question;
for there is nothing unusual in the samples themselves. On the contrary,
they are chosen because they are fairly typical of the phenomena of
reflex action in general.
In our own organization there is a reflex mechanism which ensures the
prompt withdrawal of the legs from any source of irritation supplied to
the feet. For instance, even after a man has broken his spine in such a
manner as totally to interrupt the functional continuity of his spinal
cord and brain, the reflex mechanism in question will continue to
retract his legs when his feet are stimulated by a touch, a burn, &c.
This responsive action is clearly an adaptive action, and, as the man
neither feels the stimulation nor the resulting movement, it is as
clearly a reflex action. The question now is as to the mode of its
origin and development.
I will not here dwell upon the argument from co-adaptation, because this
may be done more effectually in the case of more complicated reflex
actions, but will ask whether we can reasonably hold that this
particular reflex action--comparatively simple though it is--has ever
been of selective value to the human species, or to the ancestors
thereof? Even in its present fully-formed condition it is fairly
questionable whether it is of any adaptive _value_ at all. The movement
performed is no doubt an adaptive _movement_; but is there any occasion
upon which the reflex mechanism concerned therein can ever have been of
adaptive _use_? Until a man's legs have been paralyzed as to their
voluntary motion, he will always promptly withdraw his feet from any
injurious source of irritation by means of his conscious intelligence.
True, the reflex mechanism secures an almost inappreciable saving in the
time of response to a stimulus, as compared with the time required for
response by an act of will; but the difference is so exceedingly small,
that we can hardly suppose the saving of it in this particular case to
be a matter of any adaptive--much less selective--importance. Nor is it
more easy to suppose that the reflex mechanism has been developed by
natural selection for the purpose of replacing voluntary action when the
latter has been destroyed or suspended by grave spinal injury,
paralysis, coma, or even ordinary sleep. In short, even if for the sake
of argument we allow it to be conceivable that any single human being,
ape, or still more distant ancestor, has ever owed its life to the
possession of this mechanism, we may still be certain that not one in a
million can have done so. And, if this is the case with regard to the
mechanism as now fully constructed, still more must it have been the
case with regard to all the previous stages of construction. For here,
without elaborating the point, it would appear that a process of
construction by survival of the fittest alone is incomprehensible.