412 DARWINISM chap. 



improved races of pigs — the two latter examples being quoted 

 from Mr. Darwin, — and other cases of like nature. As 

 examples of the latter, Mr. Darwin is again quoted as 

 admitting that there are many cases in which the action of 

 similar conditions appears to have produced corresponding 

 changes in different species; and we have a very elaborate 

 discussion of the direct action of the medium in modifying the 

 protoplasm of simple organisms, so as to bring about the 

 difference between the outer surface and the inner part that 

 characterises the cells or other units of which they are formed. 

 Now, although this essay did little more than bring together 

 facts which had been already adduced by Mr. Darwin or by 

 Mr. Spencer himself, and lay stress upon their importance, its 

 publication in a popular review was immediately seized upon 

 as "an avowed and definite declaration against some of the 

 leading ideas on which the Mechanical Philosophy depends," 

 and as being "fatal to the adequacy of the Mechanical 

 Philosophy as any explanation of organic evolution," 1 — an 

 expression of opinion which would be repudiated by every 

 Darwinian. For, even admitting the interpretation which Mr. 

 Spencer puts on the facts he adduces, they are all included in 

 the causes which Darwin himself recognised as having acted 

 in bringing about the infinitude of forms in the organic world. 

 In the concluding chapter of the Origin of Species he says : 

 " 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." This passage, sum- 

 marising Darwin's whole inquiry, and explaining his final 

 point of view, shows how very inaccurate may be the popular 

 notion, as expressed by the Duke of Argyll, of any supposed 

 additions to the causes of change of species as recognised 

 by Darwin. 



1 See the Duke of Argyll's letter in Nature, vol. xxxiv. p. 336. 



