374 EEV. J. T. GULICK ON 



same environment changes its habits, learning to appropriate 

 resources that had not been previously used, it becomes a new 

 intergenerating group " in whicJi a oieio and divergent form of 

 natural selection is establislied f but that the result of the diver- 

 gence 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 disadvantageous, or even non-advantageous instincts, ever 

 persist and become the occasion of divergent selection, I re- 

 ferred to Darwin's opinion that such might be the case with 

 sexual instincts, and that the progenitors of man were deprived 

 of their hairy coat by sexual selection that was, iu its earlier 

 stages, disadvantageous. I am not aware that Darwin has ever 

 attempted to show how divergent sexual instincts arise and be- 

 come permanently fixed as distinguishing characters of varieties 

 and species. " The Advantage of Divergence," the principle on 

 which he relied to account for divergent habits, producing diver- 

 gent natural selection, he never attempted to apply here ; and, 

 above all, when he believed the newer instinct to be either non- 

 advantageous or disadvantageous, as contrasted with the older 

 instinct, he certainly could not have attributed advantage to the 

 resulting divergence. As I have pointed out on previous occa- 

 sions, Darwin assumed a psychological divergence in the sexual 

 instincts of a species in order to account for the divergence in 

 their secondary sexual characters relating to form, colour, &c. ; 

 and as there is no reason given why the psychological divergence 

 should take place, or why it should precede the change in form 

 and colour, the theory of Sexual Selection, as presented by 

 Darwin, is incomplete and unsatisfactory, especially in its rela- 

 tions to divergent evolution. If he had thrown light on the 

 causes of divergence in sexual instincts, he would have found the 

 same or similar principles applicable to the explanation of diver- 

 gence of all kinds. But my object in referring to his opinion here 

 is to point out that he was free to adm.it that permanent diver- 

 gence in sexual instincts may be non-advantageous, or even some- 

 what disadvantageous; and if this is true of sexual instincts, I 

 do not see why it may not be equally true of industrial instincts. 

 I think there is ample evidence that, when segregation has been 

 established, divergence which is neither advantageous nor disad- 

 vantageous often arises in industrial as well as other instincts, 

 and that these instincts may introduce new forms of natural, 



