Now, with regard to this pa.s.sage 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 pa.s.sages 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 s.e.xual selection, by which characters of use to one s.e.x are often gained and then transmitted more or less perfectly to the other s.e.x, though of no use to this s.e.x. 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 a.s.signed 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 pa.s.sage 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 acc.u.mulated through s.e.xual selection in relation to the propagation of the species, and through natural selection in relation to the general purposes of life. Hence, _secondary s.e.xual characters, when equally transmitted to both s.e.xes, can be distinguished from ordinary specific characters, only by the light of a.n.a.logy_. The modifications acquired through s.e.xual selection are often so strongly p.r.o.nounced that the two s.e.xes 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 s.e.xual selection, he incurs the burden of proving utility (in the life-preserving sense) in all these "frequently" occurring cases where there are such "strongly p.r.o.nounced 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 s.e.xual selection, we must accept it as Darwin"s opinion--first, that in their beginnings, as _specific_ characters, these s.e.xual 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 acc.u.mulated through _s.e.xual_ 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 pa.s.s 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 a.n.a.logous 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 pa.s.sage goes on to say, "even such structures have often, we may feel a.s.sured, 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 acc.u.mulated 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 cla.s.sification, 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 pa.s.sage 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. x.x.xix.
p. 127), Mr. Thiselton Dyer says of my interpretation of this pa.s.sage, "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 pa.s.sage with sufficient care to note the points which I have now explained.
Here is another pa.s.sage to the same general effect. In alluding to the objection from inutility as advanced by Bronn, Broca, and Nageli, 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 cla.s.sification, 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 a.s.sumes high value [i.e. for purposes of cla.s.sification]; 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 cla.s.sification[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 a.s.sumption 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 pa.s.sages 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 emanc.i.p.ated 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 pa.s.sages 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 pa.s.sages 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 pa.s.sages 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 bia.s.sed in this matter might, perhaps, be expected. After rendering the following very unequivocal pa.s.sage 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 pa.s.sage 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 pa.s.sage 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 acc.u.mulate--Darwin is emphatic in his a.s.sertion 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."