Feb. I7> 1887] 



NATURE 



363 



mental question so ably discussed .by Mr. Spencer. As 

 he remarks, " Nowadays most naturalists are more 

 Darwinian than Mr. Darwin himself," by which he means 

 that most naturalists attribute more to the agency of 

 natural selection than was attributed to it by the final 

 judgment of its discoverer. The reason of this is that 

 most naturalists have neither read with any care the later 

 editions of Mr. Darwin's works, nor probably even so much 

 as heard of the sundry essays which led him to modify 

 his views upon the comparative importance of natural 

 selection and other factors of organic evolution. Such 

 naturalists, therefore, are not true Darwinians. Stil' 

 believing in natural selection as almost the only factor of 

 organic evolution, they are archaic enough to suppose 

 that distinctions of specific value are almost universally 

 of an adaptive kind. In this respect, indeed, they share 

 what is no doubt still the popular impression of Darwinism, 

 but an impression, ne%'erthele3s, which does a great in- 

 justice to the genius of their master. In order that there 

 may be no mistake upon this matter, we will here supply 

 a few quotations from the latest editions of Mr. Darwin's 

 works, over and above the numerous extracts which Mr. 

 Spencer has selected for the same purpose. 



" I now admit, after reading the essay by NUgeli on 

 plants, and the remarks recently made by various authors 

 with respect to animals, more especially those recently 

 made by I'rof. 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 struc- 

 ture ; but I am convinced, from the light gained during 

 even the last few years, that very many structures 

 which now appear to us useless will hereafter be proved 

 to be useful, and will, therefore, come under the range of 

 natural selection. Nevertheless, I did not formerly con- 

 sider sufficiently the existence of structures, which, so 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.' (" Descent of 

 Man," 2nd edition, p. 61. He goes on to explain how 

 he was led to the "tacit assumption that every detail 

 of structure, excepting rudiments, was of some special, 

 though unrecognised, service," and concludes by remark- 

 ing that "any one with this assumption in his mind would 

 naturally extend too far the action of natural selection.") 



" In the earlier editions of this work I underrated, as it 

 now seems probable, the frequency and importance of 

 modifications due to spontaneous variability ' 1^" Origin of 

 Species," 6ih edition, p. 171). " 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 subse- 

 quently, 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 misrepre- 

 sentation ; but the history of science shows that fortun- 

 ately this power does not long endure" {Ibid. p. 421). 



" 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. 



. . . A structure, whatever it may be, which is common to 

 many allied forms, is ranked by us as of high systematic 

 importance, and consequently is often assumed to be of 

 high vital importance to the species. Thus,as I am inclined 

 to believe, morphological differences, which we consider 

 as important— such as the arrangement of leaves, the 

 division of the flower or of the ovarium, the position of 

 the ovules, &c. — first appeared in many cases as fluctuat- 

 ing variations, which sooner or later became constant 

 through the nature of the organism and of the surrounding 

 conditions, but not through natural selection ; for, as these 

 morphological characters do not affect the welfare of the 

 species, any slight deviation in them could not have been 

 governed or accumulated through this latter agency " 

 {Ibid. pp. 175, 176). 



These quotations are added to those which have bee^^ 

 supplied by Mr. Spencer, in order still further to advance 

 the " motive " with the expression of which his essay con- 

 cludes. After directing attention to the present views of 

 Prof. Huxley upon the subject — viz. " How far natural 

 selection suffices for the production of species remains to 

 be seen " ; and " Science commits suicide when it adopts 

 a creed " — Mr. Spencer closes with the following 

 remarks : — 



" Along with larger motives, one motive which has 

 joined in prompting the foregoing articles has been the 

 desire to point out that already among biologists the 

 beliefs concerning the origin of species have assumed too 

 much the character of a creed ; and that while becoming 

 settled they have become narrowed. So far from further 

 broadening that broader view which Mr. Darwin reached 

 as he grew older, his followers appear to have retrograded 

 towards a more restricted view than he ever expressed. 

 Thus there seems occasion for recognising the warning 

 uttered by Prof. Huxley as not uncalled for. Whatever 

 may be thought of the arguments and conclusions set 

 forth in this article and the preceding one, they will 

 perhaps serve to show that it is as yet far too soon 

 to close the inquiry concerning the causes of organic 

 evolution." 



Of these two articles the first is devoted to a con- 

 sideration of use and disuse as causes of such evolution, 

 while the second treats of the influence of surrounding 

 conditions. The latter is the more highly speculative, and 

 therefore may be here considered in fewer words. The idea 

 is that all external parts of organisms, being exposed to 

 different physical conditions from the internal parts, must 

 be differently affected thereby : natural selection apart, 

 there must here be recognised the differentiating agency 

 of a direct or purely physical kind. Hence a certain 

 rough analogy is drawn between a cell-wall, or cuticle, 

 and the oxidised e.xterior of an inorganic body. Many of 

 the difterentiations undergone by the epiblast in the course 

 of organic evolution may, it is argued, be best explained 

 by the immediate action of external agencies — ^just as we 

 know that a surface of mucous membrane, when brought 

 into permanent relation with such agencies, changes front 

 cylinder epithelium to squamous epithelium: "the effect 

 ' of the medium is so great that, in a short time, it over- 

 comes the inherited proclivity, and produces a structure of 

 opposite kind to the normal one." Many other examples 

 of the same general principle are given ; but the essay as 

 a whole is ingenious rather than convincing. Not, of 

 course, that we dispute the principle — which, indeed, is 

 recognised by Mr. Darwin, in one of the passages above 

 quoted, and elsewhere — but it is of too general a kind to 



