8 J. T. Gulick — Inconsistencies of Utilitarianism. 



the failure of the few individuals to completely represent the 

 average character of the species and by their being freed from 

 competition, and wide interbreeding with those of their own 

 kind, that divergent habits of feeding are formed. I further 

 claim that for the production of this result it is not at all 

 necessary that the environments presented in the isolated 

 districts should differ in any respect. Indeed if all but one 

 pair of a variable species should be destroyed, the descendants 

 of that pair, remaining in the same area and under the same 

 environment, would probably differ more or less from the 

 original stock. Those that breed together must have habits 

 that enable them to do so ; and the offspring of those that 

 interbreed widely will for the most part, inherit the powers 

 and habits that enabled their ancestors to interbreed widely ; 

 but if the offspring of a single family are carried to an isolated 

 area presenting the same environment, there will be nothing to 

 ensure the perpetuation of exactly the original powers and 

 habits, unless the power of heredity is such that each pair is 

 sure to transmit the complete average character of the whole 

 species ; and this is not the condition of all species that pair, 

 if of any. Within the limits of each freely interbreeding 

 portion of a species a mutual harmony and adjustment of 

 habits is preserved, because it is the condition of propagation 

 within those limits ; but between portions that are prevented 

 from interbreeding there is nothing but heredity to prevent 

 divergence in the kinds of adjustment ; and in variable species, 

 the probability is that divergence will in time show itself more 

 or less distinctly. Though Mr. Wallace considers this reason- 

 ing fallacious when applied to divergence in habits he uses an 

 exactly parallel reasoning in the portion of the following pas- 

 sage which I designate by italics. " It appears as if fertility 

 depended on such a delicate adjustment of the male and., fe- 

 male elements to each other, that, unless constantly kept up by 

 the preservation of the most fertile individuals, sterility is 

 always liable to arise. . . . So long as a species remains un- 

 divided, and in occupation of a continuous area, its fertility 

 is kept up by natural selection ; but the moment it becomes 

 separated, either by geographical or selective isolation, or by 

 diversity of station or of habits, while each portion must be 

 kept fertile inter se, there is nothing to prevent infertility 

 arising betxoeen the two separated portions. As the two por- 

 tions will necessarily exist under somewhat different conditions 

 of life, and will usually have acquired some diversity of form 

 and c3lor — both which circumstances we know to be either the 

 cause of infertility or to be corelated with it — the fact of some 

 degree of infertility usually appearing between closely allied 

 but locally or physiologically segregated species is exactly 



