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. 
