236 APPENDIX II—INTENSIVE SEGREGATION. 
2. Reply to Criticism. 
In view of the examples of divergence that have been discussed in 
this paper, I think I may state, as in my previous paper, ‘‘It is, 
therefore, evident, that the simple fact of divergence in any case is 
not sufficient ground for assuming that the divergent form has an 
advantage over the type from which it diverges.”* Mr. Wallace 
has criticized this statement,} using the following words: 
It seems to me that throughout his paper Mr. Gulick omits the consideration of 
the inevitable agency of natural selection, arising from the fact of only a very 
small proportion of the offspring produced each year possibly surviving. * * #* 
He omits from all consideration the fact that at each step of the divergence there 
was necessarily selection of the fit and less fit to survive; and that if, as a fact, 
the two extremes have survived, and not the intermediate steps that led to one or 
both of them, it is a proof that both had an advantage over the original less special- 
ized form. 
But what if the type from which the new form diverges is surviving at 
the same time that the newform survives? And what if both the forms 
are surrounded by the same environment which they use in different 
ways? Where, then, is the proof that the newer form has an advan- 
tage over theolderform? ‘This was the class of facts I had been consider- 
ing in the preceding paragraphs, which led to the conclusion criti- 
cized by Mr. Wallace; and instead of omitting ‘‘the consideration of 
the inevitable agency of selection,’”’ it was the very thing I was con- 
sidering. I had pointed out that when a segregated portion ofa 
species exposed to the same environment changes its habits, learning 
to appropriate resources that had not been previously used, it be- 
comes a new intergenerating group ‘‘7n which a new and divergent 
form of selection ts established,” but that the result of the divergence 
thus produced is not necessarily advantageous, and may for many 
generations be somewhat disadvantageous. As I was aware that 
many naturalists would consider it absurd to suppose that disadvan- 
tageous or even non-advantageous instincts ever persist and become 
the occasion of divergent selection, I referred to Darwin’s opinion 
that such might be the case with sexual instincts, and that the pro- 
genitors of man were deprived of their hairy coat by sexual selection 
that was, in its earlier stages, disadvantageous. Iam not aware that 
Darwin has ever attempted to show how divergent sexual instincts 
arise and become permanently fixed as distinguishing characters of 
varieties and species. 
* Linnean Society’s Journal, Zodlogy, vol. Xx, p. 214. 
t+ Nature, vol. XXXVIII, p. 491. 
