138 
On the Inconsistencies of Utilitarianism. 
Segregation produces Domestic Races , why not Species ? 
Mr. Wallace seems to be opposed to the idea that some form 
of isolation is essential to divergence ; but in his argument he 
yields so much that I cannot but think his opposition is largely 
due to his misinterpreting the theory. Mr. Romanes has 
mentioned eight or ten forms of isolation, and Mr. Wallace 
says I have discussed thirty-eight forms ; but neither of us 
claim that these are the only possible forms, nor do we claim 
that any form of this principle is essential to the transforma- 
tion of one species into another when the original one disap- 
pears in the process. The phrase “ new species ” as used by 
Mr. Wallace in the following passage is ambiguous ; but the 
second sentence seems to indicate that he is here discussing 
divergence as well as simple transformation. He says : — 
“ Most writers consider the isolation of a portion of a species a 
very important factor in the formation of new species, while 
others maintain it to be absolutely essential. This latter view 
has arisen from an exaggerated opinion as to the power of 
intercrossing to keep down any variety or incipient species 
and merge it in the parent stock. But it is evident that this 
can only occur with varieties that are not useful, or which, if 
useful, occur in very small numbers.” . . . (p. 144). Near 
the end of the same chapter, after presenting arguments in 
favour of this position, and after reviewing some of the facts 
which I have presented concerning the divergences of Sand- 
wich-Island land-molluscs, he remarks: — “We have, how- 
ever, seen reason to believe that geographical or local isolation 
is by no means essential to the differentiation of species, 
because the same result is brought about by the incipient 
species acquiring different habits or frequently a different 
station, and also by the fact that different varieties of the same 
species are known to prefer to pair with their like, and thus 
to bring about a physiological isolation of the most effective 
kind” (p. 150). Except that he has used “physiological 
isolation ” where I should have used psychological segrega- 
tion, this last passage is as completely in accord with what I 
have presented in my paper on “ Divergent Evolution ” as it 
could have been if he had copied my statements. But how 
is this passage and one of similar import on page 185 to be 
reconciled with his own statement just quoted from page 144 ? 
On pages 217, 218, and 226, he bases his argument for the 
importance of different coloration in closely allied species on 
the obvious necessity for means “ to secure the pairing 
together of individuals of the same species,” if a new species 
is to be kept “ separate from its nearest allies.” He here 
