Chapter XIV: Appendix: II (1)

ON CHARACTERS AS ADAPTIVE AND SPECIFIC.

It is the object of this Appendix to state, more fully than in the text, the opinions with regard to this subject which have been published by the two highest authorities on the theory of natural selection--Darwin and Professor Huxley. I will take first the opinion of Professor Huxley, quoted _in extenso_, and then consider it somewhat more carefully than seemed necessary in the text.

As far as I am aware, the only occasion on which Professor Huxley has alluded to the subject in question, is in his obituary notice of Darwin in the _Proceedings of the Royal Society_, Vol. XLIV, No. 269, p. xviii. The allusion is to my paper on _Physiological Selection_, in the _Journal of the Linnaean Society_, Zool. Vol. XIX, pp. 337-411. But it will be observed that the criticism has no reference to the theory which it is the object of that paper to set forth. It refers only to my definition of the theory of natural selection as primarily a theory of the origin, or cumulative development, of adaptations. This criticism, together with my answer thereto at the time, is conveyed in the following words.

"Every variety which is selected into a species is favoured and
preserved in consequence of being, in some one or more respects,
better adapted to its surroundings than its rivals. In other words,
every species which exists, exists in virtue of adaptation, and
whatever accounts for that adaptation accounts for the existence of
the species. To say that Darwin has put forward a theory of the
adaptation of species, but not of their origin, is therefore to
misunderstand the first principles of the theory. For, as has been
pointed out, it is a necessary consequence of the theory of
selection that every species must have some one or more structural
or functional peculiarities, in virtue of the advantage conferred
by which it has fought through the crowd of its competitors, and
achieved a certain duration. In this sense, it is true that every
species has been 'originated' by selection."

Now, in the first place, I have nowhere said that "Darwin has put
forward a theory of the adaptation of species, but not of their
origin." I said, and continue to say, that he has put forward a
theory of _adaptations in general_, and that where such adaptations
appertain to species only (i.e. are peculiar to particular
species), the theory becomes "_also_ a theory of the origin of the
species which present them." The only possible misunderstanding,
therefore, which can here be alleged against me is, that I fail to
perceive it as a "necessary consequence of the theory of selection
that _every_ species _must_ have some one or more structural or
functional _peculiarities_" of an adaptive or utilitarian kind.
Now, if this is a misunderstanding, I must confess to not having
had it removed by Mr. Huxley's exposition.

The whole criticism is tersely conveyed in the form of two sequent
propositions--namely, "Every species which exists, exists in virtue
of adaptation; and whatever accounts for that adaptation accounts
for the existence of the species." My answer is likewise two-fold.
First, I do not accept the premiss; and next, even if I did, I can
show that the resulting conclusion would not overturn my
definition. Let us consider these two points separately, beginning
with the latter, as the one which may be most briefly disposed of.

I. Provisionally conceding that "every species which exists, exists
in virtue of adaptation," I maintain that my definition of the
theory of natural selection still holds good. For even on the basis
of this concession, or on the ground of this assumption, the theory
of natural selection is not shown to be "_primarily_" a theory of
the origin of species. It follows, indeed, from the assumption--is,
in fact, part and parcel of the assumption--that all species have
been originated by natural selection; but why? _Only because
natural selection has originated those particular adaptive features
in virtue of which (by the hypothesis) species exist as species._
It is only in virtue of having created these features that natural
selection has created the species presenting them--just as it has
created genera, families, orders, &c., in virtue of _other_
adaptive features extending through progressively wider areas of
taxonomic division. Everywhere and equally this principle has been
"primarily" engaged in the evolution of adaptations, and if one
result of its work has been that of enabling the systematist to
trace lines of genetic descent under his divisions of species,
genera, and the rest, such a result is but "secondary" or
"incidental."

In short, it is "_primarily_" a theory of adaptations _wherever
these occur_, and only becomes "_also_" or "_incidentally_" a
theory of species in cases where adaptations happen to be
restricted in their occurrence to organic types of a certain order
of taxonomic division.

II. Hitherto, for the sake of argument, I have conceded that, in
the words of my critic, "it is a necessary consequence of the
theory of selection that every species must have some one or more
structural or functional peculiarities" of an adaptive kind. But
now I will endeavour to show that this statement does not "follow
as a necessary consequence" from "the theory of selection."

Most obviously "it follows" from the theory of selection that
"every variety which is selected into a species is favoured and
preserved in consequence of being, in some one or more respects,
better adapted to its surroundings than its rivals." This, in fact,
is no more than a re-statement of the theory itself. But it does
_not_ follow that "every species which exists, exists in virtue of
adaptation" _peculiar to that species_; i.e. that every species
which exists, exists _in virtue of having been "selected_." This
may or may not be true as a matter of fact: as a matter of logic,
the inference is not deducible from the selection theory. Every
variety which is "_selected into_" a species must, indeed, present
some such peculiar advantage; but this is by no means equivalent to
saying, "in other words," that every variety which _becomes_ a
species must do so. For the latter statement imports a completely
new assumption--namely, that every variety which _becomes_ a
species must do so because it has been "_selected into_" a species.
In short, what we are here told is, that if we believe the
selection principle to have given origin to some species, we must
further believe, "as a necessary consequence," that it has given
origin to all species.

The above reply, which is here quoted _verbatim_ from _Nature_, Vol. 38, p. 616-18, proceeded to show that it does not belong to "the first principles of the theory of natural selection" to deny that no other cause than natural selection can possibly be concerned in the origin of species; and facts were given to prove that such unquestionably has been the case as regards the origin of "local" or "permanent" _varieties_. Yet such varieties are what Darwin correctly terms "incipient" species, or species in process of taking _origin_. Therefore, if Professor Huxley's criticism is to stand at all, we must accept it "as a necessary consequence of the theory of selection," that every such _variety_ "which exists, exists in virtue of adaptation"--a statement which is _proved_ to be untrue by the particular cases forthwith cited. But as this point has been dealt with much more fully in the text of the present treatise, I shall sum up the main points in a few words.

The criticism is all embodied in two propositions--namely, (_a_) that the theory of natural selection carries with it, as a "necessary consequence," the doctrine that survival of the fittest has been the cause of the origin of _all_ species; and (_b_) that therefore it amounts to one and the same thing whether we define the theory as a theory of species or as a theory of adaptations. Now, as a mere matter of logical statement, it appears to me that both these propositions are unsound. As regards the first, if we hold with Darwin that other causes have co-operated with natural selection in the origination of some (i. e. many) species, it is clearly no part of the theory of natural selection to assume that none of these causes can ever have acted independently. In point of fact, as we have seen in the foregoing chapters, such has probably and frequently been the case under the influences of isolation, climate, food, sexual selection, and laws of growth; but I may here adduce some further remarks with regard to yet another possible cause. If the Lamarckian principles are valid at all, no reason can be shown why in some cases they may not have been competent _of themselves_ to induce morphological changes of type by successive increments, until a transmutation of species is effected by their action alone--as, indeed, Weismann believes to have been the case with all the species of Protozoa[148]. That such actually has often been the case also with numberless species of Metozoa, is the belief of the neo-Lamarckians; and whether they are right or wrong in holding this belief, it is equally certain that, _as a matter of logical reasoning_, they are not compelled by it to profess any _disbelief_ in the agency of natural selection. They may be mistaken as to the facts, as Darwin in a lesser degree may have been similarly mistaken; but just as Darwin has nowhere committed himself to the statement that _all_ species must _necessarily_ have been originated by natural selection, so these neo-Lamarckians are perfectly logical in holding that _some_ species may have been wholly caused by the inheritance of acquired characters, as _other_ species may have been wholly caused by the natural selection of congenital characters. In short, unless we begin by assuming (with Wallace and against Darwin) that there _can be no other cause_ of the origin of species than that which is furnished by natural selection, we have no basis for Professor Huxley's statement "that every species has been originated by selection"; while, if we do set out with this assumption, we end in a mere tautology. What ought to be done is to prove the validity of this assumption; but, as Professor Huxley makes no attempt to do this, his criticism amounts to mere begging of the question.

[148] Since the above was written Professor Weismann has transferred
this doctrine from the Protozoa to their ancestors.

And now, as regards the second point (_b_), even if we grant the assumption that natural selection is the only possible cause of the origin of species--or, which is the same thing, that every species has been originated by natural selection,--is it likewise the same thing whether we define the theory of natural selection as a theory of species or as a theory of adaptations? Professor Huxley's criticism endeavours to show that it is; but a little consideration is enough to show that it is not. What does follow from the assumption is, that, _so far as specific characters are concerned_, it is one and the same thing to say that the theory is a theory of species, and to say that it is a theory of adaptations. But specific characters are not conterminous with adaptive characters; for innumerable adaptive characters are not distinctive of species, but of genera, families, orders, classes, and sub-kingdoms. Therefore, if it is believed (as, of course, Professor Huxley believes) that the theory in question explains the evolution of all adaptive characters, obviously it is not one and the same thing to define it indifferently as a theory of species or as a theory of adaptations.

Now, all this is not merely a matter of logic chopping. On the contrary, the question whether we are to accept or to reject the deduction that all species must necessarily have owed their origin to natural selection, is a question of no small importance to the general theory of evolution. And our answer to this question must be determined by that which we give to the ulterior question--Is the theory of natural selection to be defined as a theory of species, or as a theory of adaptations?

* * * * *

We now pass on to our consideration of Darwin's opinion touching the question, as stated by himself,--"The doctrine of utility, how far true?" As I cannot ascertain that Darwin has anywhere expressed an opinion as to whether natural selection has been necessarily concerned in the origin of all _species_, the issue here is as to whether he held this with regard to all _specific characters_. It will be remembered that while opposing this doctrine as erroneous both in logic and in fact, I have represented that it is not a doctrine which Darwin sanctioned; but, on the contrary, that it is one which he expressly failed to sanction, by recognizing the frequent inutility of specific characters. Mr. Wallace, on the other hand, alleges that Darwin did believe in the universal--as distinguished from the general--utility of such characters. And he adds that he has "looked in vain in Mr. Darwin's works" for any justification of my statements to the contrary[149]. Therefore I will endeavour to show that Mr. Wallace's search has not been a very careful one.

[149] _Darwinism_, p. 131. He says:--"I have looked in vain in Mr.
Darwin's works for any such acknowledgement" (i.e. "that a
large proportion of specific distinctions must be conceded
useless to the species presenting them").

We must remember, however, that it was not until the appearance of my paper on _Physiological Selection_, four years after Darwin's death, that the question now in debate was raised. Consequently, he never had occasion to deal expressly with this particular question--viz. whether "the doctrine of utility" has any _peculiar_ reference to _specific_ characters--as he surely would have done had he entertained the important distinction between specific and all other characters which Mr. Wallace now alleges that he did entertain. But, be this as it may, we cannot expect to find in Darwin's writings any express allusion to a question which had not been raised until 1886. The most we can expect to find are scattered sentences which prove that the distinction in question was never so much as present to his mind,--i. e. never occurred to him as even a possible distinction.

I will first take the passages which Mr. Wallace himself supplies from among those which I had previously indicated.

"But when, from the nature of the organism and of the conditions,
modifications have been induced which are unimportant for the
welfare of the _species_, they may be, and apparently often have
been, transmitted in nearly the same state to numerous, otherwise
modified, descendants[150]."

[150] _Origin of Species_, p. 175. Italics mine.

On this passage Mr. Wallace remarks that the last five words "clearly show that such characters are usually not 'specific,' in the sense that they are such as distinguish species from one another, but are found in numerous allied species." But I cannot see that the passage shows anything of the sort. What to my mind it does show is, (_a_) that Mr. Darwin repudiated Mr. Wallace's doctrine touching the _necessary_ utility of _all_ specific characters: (_b_) that he takes for granted the contrary doctrine touching the inutility of _some_ specific characters: (_c_) that without in this place alluding to the proportional number of useless specific characters, he refers their origin in some cases to "the nature of the organism" (i.e. "spontaneous variability" due to internal causes), and in other cases to "the conditions" (i.e. variability induced by external causes): (_d_) that when established as a specific character by heredity, such a useless character was held by him not to tend to become obsolete by the influence of natural selection or any other cause; but, on the contrary, to be "transmitted in nearly the same state to numerous, otherwise modified, descendants"--or progeny of the species in genera, families, &c.: (_e_) and, therefore, that useless characters which are now distinctive of genera, families, &c., were held by him frequently, if not usually, to point to uselessness of origin, when first they arose as merely specific characters. Even the meaning which Mr. Wallace reads into this passage must imply every one of these points; and therefore I do not see that he gains much by apparently seeking to add this further meaning--viz. that in Darwin's opinion there must have been some unassignable reason preventing the occurrence of useless specific characters in cases where species are _not_ destined to become the parents of genera.

Moreover, any such meaning is out of accordance with the context from which the passage is taken. For, after a long consideration of the question of utility, Darwin sums up,--"We thus see that with plants many morphological changes may be attributed to the laws of growth and the interaction of parts, _independently of natural selection_." And then he adds,--"From the fact of the above characters being _unimportant for the welfare of the species_, any slight variations which occurred in them _would not have been augmented through natural selection_." Again, still within the same passage, he says, while alluding to the causes other than natural selection which lead to changes of specific characters,--"If the _unknown cause_ were to act almost uniformly for a length of time, we may infer that the result would be almost uniform; and in this case _all_ the individuals of the _species_ would be modified in the same manner." For my own part I do not understand how Mr. Wallace can have overlooked these various references to _species_, all of which occur on the very page from which he is quoting. The whole argument is to show that "many morphological changes may be attributed to the laws of growth and the inter-action of parts [_plus_ external conditions of life], independently of natural selection"; that such non-adaptive changes, when they occur as "specific characters," may, if the species should afterwards give rise to genera, families, &c., become distinctive of these higher divisions. But there is nothing here, or in any other part of Darwin's writings, to countenance the inconsistent notion which Mr. Wallace appears to entertain,--viz. that species which present useless characters are more apt to give rise to genera, families, &c., than are species which do not present such characters.

The next passage which Mr. Wallace quotes, with his comments thereon, is as follows. The italics are his.

"'Thus a large yet undefined extension may safely be given to the
direct and indirect results of natural selection; but I now admit,
after reading the essay of Naegeli on plants, and the remarks by
various authors with respect to animals, more especially those
recently made by Professor Broca, that in the earlier editions of
my Origin of Species I perhaps attributed too much to the action of
natural selection, or the survival of the fittest. I have altered
the fifth edition of the Origin so as to confine my remarks to
adaptive changes of structure; _but I am convinced, from the light
gained during even the last few years, that very many structures
which now appear to be useless, will hereafter be proved to be
useful, and will therefore come within the range of natural
selection_. Nevertheless I did not formerly consider sufficiently
the existence of structures which, as far as we can at present
judge, are neither beneficial nor injurious; and this I believe to
be one of the greatest oversights as yet detected in my work.'

Now it is to be remarked that neither in these passages nor in any
of the other less distinct expressions of opinion on this question,
does Darwin ever admit that "specific characters"--that is, the
particular characters which serve to distinguish one species from
another--are ever useless, much less that "a large proportion of
them" are so, as Mr. Romanes makes him "freely acknowledge." On the
other hand, in the passage which I have italicised he strongly
expresses his view that much of what we suppose to be useless is
due to our ignorance; and as I hold myself that, as regards many of
the supposed useless characters, this is the true explanation, it
may be well to give a brief sketch of the progress of knowledge in
transferring characters from the one category to the other[151]."

[151] _Darwinism_, p. 132.

It is needless to continue this quotation, because of course no one is disputing that an enormous number of specific characters whose utility is unknown are nevertheless useful, and therefore due to natural selection. In other words, the question is not--Are there not many useful specific characters whose utility is unknown? but--Does it follow from the theory of natural selection that all specific characters must necessarily be useful? Well, it appears to me that without going further than the above passage, which Mr. Wallace has quoted, we can see clearly enough what was Darwin's opinion upon the subject. He did not believe that it followed _deductively_ from his theory that all specific characters must necessarily be useful; and therefore he regarded it as a question of _fact_--to be determined by induction as distinguished from deduction--in what proportional number of cases they are so. Moreover he gives it as his more matured opinion, that, "as far as we can at present judge" (i.e. from the present state of observation upon the subject: if, with Mr. Wallace, his judgement were _a priori_, why this qualification?), he had not previously sufficiently considered the existence of non-adaptive characters--and this he ended by believing was one of the greatest oversights as yet detected in his work. To me it has always seemed that this passage is one of the greatest exhibitions of candour, combined with solidity of judgement, that is to be met with even in the writings of Darwin. There is no talk about any deductive "necessity"; but a perfect readiness to allow that causes other than natural selection may have been at work in evoking non-adaptive characters, so that the fifth edition of the _Origin of Species_ was altered in order to confine the theory of natural selection to "adaptive changes"--i.e. to constitute it, as I have said in other words, "a theory of the origin, or cumulative development, of _adaptations_."

If to this it be said that in the above passage there is no special mention of _species_, the quibble would admit of a three-fold reply. In the first place, the quibble in question had never been raised. As already stated, it is only since the appearance of my own paper on _Physiological Selection_ that anybody ever thought of drawing a distinction between species and genera, such that while all specific characters must be held necessarily useful, no such necessity extends to generic characters. In the second place, that Darwin must have had specific characters (as well as generic) in his mind when writing the above passage, is rendered unquestionable by the fact that many of the instances of inutility adduced by Naegeli and Broca have reference to specific characters. Lastly, as shown in the passages previously quoted from the sixth edition of the _Origin of Species_, Darwin attributed the origin of useless generic characters to useless specific characters; so that Mr. Wallace really gains nothing by his remark that specific characters are not specially mentioned in the present passage.

Once more:--

"Darwin's latest expression of opinion on this question is
interesting, since it shows he was inclined to return to his
earlier view of the general, or universal, utility of specific
characters[152]."

[152] _Darwinism_, p. 142.

This "latest expression of opinion," as I shall immediately prove, shows nothing of the kind--being, in fact, a mere re-statement of the opinion everywhere and at all times expressed by Darwin, touching the caution that must be observed in deciding, _with respect to individual cases_, whether an apparently useless specific character is to be regarded as really useless. Moreover, at no time and in no place did Darwin entertain any "view of the general, or universal, utility of specific characters." But the point now is, that if (as was the case) Darwin "inclined" to depart more and more from his earlier view of the highly _general_ utility of specific characters; and if (as was not the case) he ended by showing an inclination "_to return_" to this earlier view; what becomes of the whole of Mr. Wallace's contention against which this Appendix is directed, namely, _that Darwin never entertained any other view than that of the "general, or universal, utility of specific characters_"?

The "latest expression of opinion" which Mr. Wallace quotes, occurs in a letter written to Professor Semper in 1878. It is as follows:--

"As our knowledge advances, very slight differences, considered by
systematists as of no importance in structure, are continually
found to be functionally important; and I have been especially
struck with this fact in the case of plants, to which my
observations have of late years been confined. Therefore it seems
to me rather rash to consider the slight differences between
representative species, for instance those inhabiting the different
islands of the same archipelago, as of no functional importance,
and as not in any way due to natural selection[153]."

[153] _Life and Letters_, vol. iii. p. 161.

Now, with regard to this passage it is to be observed, as already remarked, that it refers to the formation of final judgements touching _particular cases_: there is nothing to show that the writer is contemplating _general principles_, or advocating on deductive grounds the dogma that specific characters must be necessarily and universally adaptive characters. Therefore, what he here says is neither more nor less than I have said. For I have always held that it would be "rather rash" to conclude that any given cases of apparent inutility are certainly cases of real inutility, _merely on the ground that utility is not perceived_. But this is clearly quite a distinct matter from resisting the _a priori_ generalization that all cases of apparent inutility must certainly be cases of real utility. And, I maintain, in every part of his writings, without any exception, where Darwin alludes to this matter of general principle, it is in terms which directly contradict the deduction in question. As the whole of this Appendix has been directed to proving that such is the case, it will now, I think, be sufficient to supply but one further quotation, in order to show that the above "latest expression of opinion," far from indicating that in his later years Darwin "inclined" to Mr. Wallace's views upon this matter, is quite compatible with a distinct "expression of opinion" to the contrary, in a letter written less than six years before his death.

"In my opinion _the greatest error which I have committed_, has
been not allowing sufficient weight to the direct action of the
environment, i.e. food, climate, &c., _independently of natural
selection_. Modifications thus caused, _which are neither of
advantage nor disadvantage to the modified organisms_, would be
especially favoured, as I can now see chiefly through your
observations, _by isolation in a small area, where only a few
individuals lived under nearly uniform conditions_[154]."

[154] _Life and Letters_, vol. iii. p. 158.

I will now proceed to quote further passages from Darwin's works, which appear to have escaped the notice of Mr. Wallace, inasmuch as they admit of no doubt regarding the allusions being to _specific_ characters.

"_We may easily err in attributing importance to characters, and in
believing that they have been developed through natural selection._
We must by no means overlook the effects of the definite action of
changed conditions of life,--of so-called spontaneous variations,
which seem to depend in a quite subordinate degree on the nature of
the conditions,--of the tendency to reversion to long-lost
characters,--of the complex laws of growth, such as of
correlation[155], compensation, of pressure of one part on another,
&c., and finally of sexual selection, by which characters of use to
one sex are often gained and then transmitted more or less
perfectly to the other sex, though of no use to this sex. But
structures thus indirectly gained, _although at first of no
advantage to a species_, may subsequently have been taken advantage
of by its modified descendants, under new conditions of life and
newly acquired habits[156]."

[155] It must be observed that Darwin uses this word, not as Mr.
Wallace always uses it (viz. as if correlation can only be
with regard to adaptive characters), but in the wider sense
that any change in one part of an organism--whether or not it
happens to be an adaptive change--is apt to induce changes in
other parts.

[156] _Origin of Species_, pp. 157-8.

It appeared--and still appears--to me, that where so many causes are expressly assigned as producing useless _specific_ characters, and that some of them (such as climatic influences and independent variability) must be highly general in their action, I was justified in representing it as Darwin's opinion that "a large proportional number of specific characters" are useless to the _species_ presenting them, although afterwards they may sometimes become of use to genera, families, &c. Moreover, this passage goes on to point out that specific characters which at first sight appear to be obviously useful, are sometimes found by fuller knowledge to be really useless--a consideration which is the exact inverse of the argument from ignorance as used by Mr. Wallace, and serves still further to show that in Darwin's opinion utility is by no means an invariable, still less a "necessary," mark of specific character. The following are some of the instances which he gives.

"The sutures in the skulls of young mammals have been advanced as a
beautiful adaptation for aiding parturition, and no doubt they may
facilitate, or be indispensable for this act; but as sutures occur
in the skulls of young birds and reptiles, which have only to
escape from a broken egg, we may infer that this structure has
_arisen from the laws of growth_, and has been taken advantage of
in the parturition of the higher animals[157]."

"The naked skin on the head of a vulture is generally considered as
a direct adaptation for wallowing in putridity; and so it may be,
_or it may possibly be due to the direct action of the putrid
matter_; but we should be very cautious in drawing any such
inference [i.e. as to utility] when we see the skin on the head of
the clean-feeding male Turkey is likewise naked[158]."

[157] _Ibid._

[158] _Origin of Species_, pp. 157-8.

Similarly, in the _Descent of Man_ it is said:--

"Variations of the same _general_ nature have _often been taken
advantage of_ and accumulated through sexual selection in relation
to the propagation of the species, and through natural selection in
relation to the general purposes of life. Hence, _secondary sexual
characters, when equally transmitted to both sexes, can be
distinguished from ordinary specific characters, only by the light
of analogy_. The modifications acquired through sexual selection
are often so strongly pronounced that the two sexes have frequently
been ranked as distinct species, or even as distinct genera[159]."

[159] _Descent of Man_, p. 615.

As Mr. Wallace does not recognize sexual selection, he incurs the burden of proving utility (in the life-preserving sense) in all these "frequently" occurring cases where there are such "strongly pronounced modifications," and we have already seen in the text his manner of dealing with this burden. But the point here is, that whether or not we accept the theory of sexual selection, we must accept it as Darwin's opinion--first, that in their beginnings, as _specific_ characters, these sexual modifications were often of a merely "_general nature_" (or without reference to utility even in the life-embellishing sense), and only _afterwards_ "have often been taken advantage of and accumulated through _sexual_ selection": and, secondly, that "we know they have been acquired in some instances _at the cost not only of inconvenience, but of exposure to actual dangers_[160]."

[160] _Ibid._

We may now pass on to some further, and even stronger, expressions of opinion with regard to the frequent inutility of _specific_ characters.

"I have made these remarks only to show that, if we are unable to
account for the characteristic differences of our several domestic
breeds, which nevertheless are generally admitted to have arisen
through ordinary generation from one or a few parent stocks, we
ought not to lay too much stress on our ignorance of the precise
cause [i.e. whether natural selection or some other cause] of the
slight analogous differences between true _species_.... I fully
admit that _many_ structures are now of no use to their possessors,
and may never have been of any use to their progenitors; but this
does not prove that they were formed solely for beauty or variety.
No doubt the definite action of changed conditions, and the various
causes of modification, lately specified, have all produced an
effect, _probably a great effect, independently of any advantage
thus gained_.... It is scarcely possible to decide how much
allowance ought to be made for such causes of change, as the
definite action of external conditions, so-called spontaneous
variations, and the complex laws of growth; but, _with these
important exceptions_, we may conclude that the structure of every
living creature either now is, or formerly was, of some direct or
indirect use to its possessor[161]."

[161] _Descent of Man_, pp. 159-60.

Here again, if we remember how "important" these "exceptions" are, I cannot understand any one doubting Darwin's opinion to have been that a large proportional number of specific characters are useless. For that it is "species" which he here has mainly in his mind is evident from what he says when again alluding to the subject in his "Summary of the Chapter"--namely, "In _many_ other cases [i.e. in cases where natural selection has not been concerned] modifications are probably the direct result of the laws of variation or of growth, independently of any good having been thus gained." Now, not only do these "laws" apply as much to species as they do to genera; "but," the passage goes on to say, "even such structures have often, we may feel assured, been subsequently taken advantage of, and still further modified, for the good of _species_ under new conditions of life." Obviously, therefore, the inutility in such cases is taken to have been prior to any utility subsequently acquired; and genera are not historically prior to the species in which they originate.

Here is another quotation:--

"Thus, as I am inclined to believe, morphological differences,
which we consider as important--such as the arrangement of the
leaves, the divisions of the flower or of the ovarium, the position
of the ovules, &c.--_first_ appeared in _many_ cases as
_fluctuating variations_, which sooner or later became constant
through the nature of the organism and of the surrounding
conditions, as well as through the intercrossing of distinct
individuals, _but not through natural selection_; for as these
morphological characters do not affect the welfare of the
_species_, any slight deviations in them could not have been
governed or accumulated through this latter agency. It is a strange
result which we thus arrive at, namely, that characters of slight
vital importance to the _species_, are the most important to the
systematist; but, as we shall hereafter see when we treat of the
genetic principle of classification, this is by no means so
paradoxical as it may at first appear[162]."

[162] _Descent of Man_, p. 176.

Clearly the view here expressed is that characters which are now distinctive of higher taxonomic divisions "first appeared" in the parent species of such divisions; for not only would it be unreasonable to attribute the rise and preservation of useless characters to "fluctuating variations" affecting a number of species or genera similarly and simultaneously; but it would be impossible that, if such were the case, they could be rendered "constant through the nature of the organism and of the surrounding conditions, as well as through the intercrossing of distinct individuals[163]."

[163] The passage to which these remarks apply is likewise quoted,
in the same connexion as above, in my paper on _Physiological
Selection_. In criticising that paper in _Nature_ (vol. xxxix.
p. 127), Mr. Thiselton Dyer says of my interpretation of this
passage, "the obvious drift of this does not relate to
specific differences, but to those which are characteristic of
family." But in making this remark Mr. Dyer could not have
read the passage with sufficient care to note the points which
I have now explained.

Here is another passage to the same general effect. In alluding to the objection from inutility as advanced by Bronn, Broca, and Naegeli, Mr. Darwin says:--"There is much force in the above objection"; and, after again pointing out the important possibility in any particular cases of hidden or former use, and the action of the laws of growth, he goes on to say,--"In the third place, we have to allow for the direct and definite action of changed conditions of life, and for so-called spontaneous variations, in which the nature of the conditions plays quite a subordinate part[164]." Elsewhere he says,--"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_[165]." The "forms of variation" to which he here alludes are "variations which seem to us in our ignorance to arise spontaneously"; and it is evident that such variations cannot well "arise" in two or more species of a genus similarly and simultaneously, so as independently to lead "to permanent modifications of structure" in two or more parallel lines. It is further evident that by "spontaneous variations" Darwin alludes to extreme cases of spontaneous departure from the general average of specific characters; and therefore that lesser or more ordinary departures must be of still greater "frequency."

[164] _Origin of Species_, p. 171.

[165] _Ibid._ p. 421.

Again, speaking of the principles of classification, Darwin writes:--

"We care not how trifling a character may be--let it be the mere
inflection of the angle of the jaw, the manner in which an
insect's wing is folded, whether the skin be covered by hair or
feathers--if it prevail throughout many and different species,
especially those having very different habits of life, it assumes
high value [i.e. for purposes of classification]; for we can
account for its presence in so many forms with such _different
habits_, only by inheritance from a common parent. We may err in
this respect in regard to single points of structure, but when
several characters, let them be ever so trifling, concur throughout
a large group of beings _having different habits_, we may feel
almost sure, on the theory of descent, that these characters have
been inherited from a common ancestor; and we know that such
aggregated characters have especial value in classification[166]."

[166] _Origin of Species_, pp. 372-373.

Now it is evident that this argument for the general theory of evolution would be destroyed, if Wallace's assumption of utility of specific characters as universal were to be entertained. And the fact of apparently "trifling" characters occurring throughout a large group of beings "having different habits" is proof that they are really trifling, or without utilitarian significance.

It is needless to multiply these quotations, for it appears to me that the above are amply sufficient to establish the only point with which we are here concerned, namely, that Darwin's opinion on the subject of utility in relation to specific characters was substantially identical with my own. And this is established, not merely by the literal meaning of the sundry passages here gathered together from different parts of his writings; but likewise, and perhaps still more, from the tone of thought which pervades these writings as a whole. It requires no words of mine to show that the literal meaning of the above quotations is entirely opposed to Mr. Wallace's view touching the _necessary_ utility of _all_ specific characters; but upon the other point--or the general tone of Mr. Darwin's thought regarding such topics--it may be well to add two remarks.

In the first place, it must be evident that so soon as we cease to be bound by any _a priori_ deduction as to natural selection being "the exclusive means of modifications," it ceases to be a matter of much concern to the theory of natural selection in what proportion other means of modification have been at work--especially when non-adaptive modifications are concerned, and where these have reference to merely "specific characters," or modifications of the most incipient kind, least generally diffused among organic types, and representing the incidence of causes of less importance than any others in the process of organic evolution considered as a whole. Consequently, in the second place, we find that Darwin nowhere displays any solicitude touching the proportional number of specific characters that may eventually prove to be due to causes other than natural selection. He takes a much wider and deeper view of organic evolution, and, having entirely emancipated himself from the former conception of species as the organic units, sees virtually no significance in specific characters, except in so far as they are also adaptive characters.

Such, at all events, appears to me the obvious interpretation of his writings when these are carefully read with a view to ascertaining his ideas upon "Utilitarian doctrine: how far true." And I make these remarks because it has been laid to my charge, that in quoting such passages as the above I have been putting "a strained interpretation" upon Darwin's utterances: "such admissions," it is said, "Mr. Romanes appears to me to treat as if wrung from a hostile witness[167]." But, from what has gone before, it ought to be apparent that I take precisely the opposite view to that here imputed. Far from deeming these and similar passages as "admissions wrung from a hostile witness," and far from seeking to put any "strained interpretation" upon them, I believe that they are but the plain and unequivocal expressions of an opinion which I have always understood that Darwin held. And if any one has been led to think otherwise, I throw back this charge of "strained interpretation," by challenging such a person to adduce a single quotation from any part of Darwin's works, which can possibly be held to indicate that he regarded passages like those above quoted as in any way out of conformity with his theory of natural selection--or as put forward merely to "admit the possibility of explanations, to which really, however, he did not attach much importance." To the best of my judgement it is only some bias in favour of Mr. Wallace's views that can lead a naturalist to view in this way the clear and consistent expression of Darwin's.

[167] Mr. Thiselton Dyer in _Nature_, _loc. cit._

That Mr. Wallace himself should be biassed in this matter might, perhaps, be expected. After rendering the following very unequivocal passage from the _Origin of Species_ (p. 72)--"There can be little doubt that the tendency to vary in the same manner has often been so strong, _that all individuals of the same species have been similarly modified without the aid of any form of selection_"--Mr. Wallace says, "But no proof whatever is offered of this statement, and it is so entirely opposed to all we know of the facts of variation as given by Darwin himself, that the important word 'all' is probably an oversight." But, if Mr. Wallace had read the very next sentence he would have seen that here the important word "all" could not _possibly_ have been "an oversight." For the passage continues,--"Or only a third, fifth, or tenth part of the individuals may have been thus affected, of which fact several instances could be given. Thus Graba estimates that about one-fifth of the guillemots in the Faroe Islands consist of a variety so well marked, that it was formerly ranked as a distinct species under the name of Uria lacrymans." And even if this passage had not been thus specially concerned with the question of the _proportion_ in which "_individuals of the same species have been similarly modified without the aid of any form of selection_" the oversight with respect to "the important word 'all'" would still have remained an oversight of a recurrent character, as the following additional quotations from other parts of Darwin's writings may perhaps render apparent.

"There must be some efficient cause for each slight individual
difference, as well as for more strongly marked variations which
occasionally arise; and if the unknown cause were to act
persistently, it is almost certain that _all_ the individuals of
the _species_ would be similarly modified[168]."

"The acquisition of a useless part can hardly be said to raise an
organism in the natural scale.... We are so ignorant of the
exciting cause of the above specified modifications; but if the
unknown cause were to act almost uniformly for a length of time, we
may infer that the result would be almost uniform; and in this case
_all_ the individuals of the _species_ would be modified in the
same manner[169]."

[168] _Origin of Species_, p. 171.

[169] _Ibid._ p. 175.

Moreover, when dealing even with such comparatively slight changes as occur between our domesticated varieties--and which, _a fortiori_, are less likely to become "stable" through the uniform operation of causes other than selection, seeing that they are not only smaller in amount than occurs among natural species, but also have had but a comparatively short time in which to accumulate--Darwin is emphatic in his assertion of the same principles. For instance, in the twenty-third chapter of the _Variation of Plants and Animals under Domestication_, he repeatedly uses the term "definite action of external conditions," and begins the chapter by explaining his use of the term thus:--

"By the term definite action, as used in this chapter, I mean an
action of such a nature that, when many individuals of the same
variety are exposed during several generations to any change in
their physical conditions of life, _all_, or _nearly all_, the
individuals are modified in the same manner. A new _sub-variety_
would thus be produced _without the aid of selection_[170]."

[170] _Variation_, &c., vol. ii. p. 260.

As an example of the special instances that he gives, I may quote the following from the same work:--

"Each of the endless variations which we see in the plumage of our
fowls must have had some efficient cause; and if the same cause
were to act uniformly during a long series of generations on many
individuals, _all_ probably would be modified in the same manner."

And, as instances of his more general statements in Chapter XXIII, these may suffice:--

"The direct action of the conditions of life, whether leading to
definite or indefinite results, _is a totally distinct
consideration from the effects of natural selection_.... The direct
and definite action of changed conditions, in contradistinction to
the accumulation of indefinite variations, _seems to me so
important_ that I will give a large additional body of
miscellaneous facts[171]."

[171] _Ibid._ vol. ii. p. 261.

Then, after giving these facts, and showing how in the case of species in a state of nature it is often impossible to decide how much we are to attribute to natural selection and how much to the definite action of changed conditions, he begins his general summary of the chapter thus:--

"There can be no doubt, from the facts given in the early part of
this chapter, that extremely slight changes in the conditions of
life sometimes act in a definite manner on our already variable
domesticated productions [productions, therefore, with regard to
which uniformity and 'stability' of modification are least likely
to arise]; and, as the action Of changed conditions in causing
general or indefinite variability is accumulative, so it may be
with their definite action. Hence it is possible that _great_ and
_definite_ modifications of structure may result from altered
conditions acting during a long series of generations. In some few
instances a marked effect has been produced quickly on _all_, or
_nearly all_, the individuals which have been exposed to some
considerable change of climate, food, or other circumstance[172]."

[172] _Variation_, &c., vol. ii. p. 280.

Once more, in order to show that he retained these views to the end of his life, I may quote a passage from the second edition of the _Descent of Man_, which is the latest expression of his opinion upon these points:--

"Each of the endless diversities in plumage, which we see in our
domesticated birds, is, of course, the result of some definite
cause; and under natural and more uniform conditions, some one
tint, _assuming that it was in no way injurious, would almost
certainly sooner or later prevail_. The free-intercrossing of the
many individuals belonging to the same species would ultimately
tend to make any change of colour thus induced _uniform in
character_.... Can we believe that the very slight differences in
tints and markings between, for instance, the female black-grouse
and red-grouse serve as a protection? Are partridges as they are
now coloured, better protected than if they had resembled quails?
Do the slight differences between the females of the common
pheasant, the Japan and golden pheasants, serve as a protection, or
might not their plumage have been interchanged with impunity? From
what Mr. Wallace has observed of the habits of certain gallinaceous
birds in the East, he thinks that such slight differences are
beneficial. For myself, I will only say, I am not convinced[173]."

[173] _Descent of Man_, pp. 473-4.

Yet "convinced" he certainly must have been on merely _a priori_ grounds, had he countenanced Mr. Wallace's reasoning from the general theory of natural selection; and the fact that he here fails to be convinced even by "what Mr. Wallace has observed of the habits of certain gallinaceous birds," appears to indicate that he had considered the question of utility with special reference to Mr. Wallace's opinion. That opinion was then, as now, the avowed result of a theoretical prepossession; and this prepossession, as the above quotations sufficiently show, was expressly repudiated by Darwin.

Lastly, this is not the only occasion on which Darwin expressly repudiates Mr. Wallace's opinion on the point in question. For it is notorious that these co-authors of the theory of natural selection have expressed divergent opinions concerning the origin by natural selection of the most general of all specific characters--cross-sterility. Although allowing that cross-sterility between allied species may be of adaptive value in "keeping incipient species from blending," Darwin persistently refused to be influenced by Wallace's belief that it is due to natural selection; i.e. the belief on which alone can be founded the "necessary deduction" with which we have been throughout concerned.

NOTE A TO PAGE 57.

I think it is desirable here to adduce one or two concrete illustrations of these abstract principles, in order to show how, as a matter of fact, the structure of Weismann's theory is such as to preclude the possibility of its assumptions being disproved--and this even supposing that the theory is false.

At first sight nothing could seem more conclusive on the side of Darwinian or Lamarckian principles than are the facts of hereditary disease, in cases where the disease has unquestionably been acquired by the parents. Take, for example, the case of gout. Here there is no suspicion of any microbe being concerned, nor is there any question about the fact of the disease being one which is frequently acquired by certain habits of life. Now, suppose the case of a man who in middle age acquires the gout by these habits of life--such as insufficient exercise, over-sufficient food, and free indulgence in wine. His son inherits the gouty diathesis, and even though the boy may have the fear of gout before his eyes, and consequently avoid over-eating and alcoholic drinking, &c., the disease may overtake him also. Well, the natural explanation of all this is, that the sins of the fathers descend upon the children; that gout acquired may become in the next generation gout transmitted. But, on the other hand, the school of Weismann will maintain that the reason why the parent contracted the gout was because he had a congenital, or "blastogenetic," tendency towards that disease--a tendency which may, indeed, have been intensified by his habits of life, but which, in so far as thus intensified, was not transmitted to his offspring. All that was so transmitted was the congenital tendency; and all that is proved by such cases as those above supposed, where the offspring of gouty parents become gouty notwithstanding their abstemious habits, is that in such offspring the congenital tendency is even more pronounced than it was in their parents, and therefore did not require so much inducement in the way of unguarded living to bring it out. Now, here again, without waiting to consider the relative probabilities of these two opposing explanations, it is enough for the purposes of the illustration to remark that it is obviously impossible to disprove either by means of the other, or by any class of facts to which they may severally appeal.