‘* Mental Evolution in Animals” 65 
in Professor Weismann’s book. There was a little some- 
thing here and there, but not much. 
It may be expected that I should say something here 
about Mr. Romanes’ latest contribution to biology—I 
mean his theory of physiological selection, of which the 
two first instalments have appeared in Nature just as these 
pages are leaving my hands, and many months since the 
foregoing, and most of the following chapters were written. 
I admit to feeling a certain sense of thankfulness that they 
did not appear earlier ; as it is, my book is too far advanced 
to be capable of further embryonic change, and this must 
be my excuse for saying less about Mr. Romanes’ theory 
than I might perhaps otherwise do. I cordially, however, 
agree with the Times, which says that ‘“‘ Mr. George 
Romanes appears to be the biological investigator on whom 
the mantle of Mr. Darwin has most conspicuously de- 
scended ’”’ (August 16, 1886). Mr. Romanes is just the 
person whom the late Mr. Darwin would select to carry on 
his work, and Mr. Darwin was just the kind of person 
towards whom Mr. Romanes would find himself instinct- 
ively attracted. 
The Times .continues—‘ The position which Mr. 
Romanes takes up is the result of his perception shared by 
many evolutionists, that the theory of natural selection is 
not really a theory of the origin of species. . . .”” What, 
then, becomes of Mr. Darwin’s most famous work, which 
was written expressly to establish natural selection as the 
main means of organic modification? ‘‘ The new factor 
which Mr. Romanes suggests,” continues the Times, “‘ is 
that at a certain stage of development of varieties in a 
state of nature a change takes place in their reproductive 
systems, rendering those\ which differ in some particulars 
mutually infertile, and thus the formation of new permanent 
species takes place without the swamping effect of free inter- 
crossing-. . . How his theory can be properly termed one 
of slrtion he fails to make clear. If correct, it is a law or 
E 
