J. T. Gulick — Inconsistencies of Utilitarianism. 9 



what we should expect" (p. 184-5). Notwithstanding this 

 statement he does not seem to have grasped the idea, that in 

 the geographically isolated portions as well as in the others, 

 the " different conditions of life " of which he speaks, may be 

 the different relations to the environment into which the 

 separated portions are brought by their divergent habits, with- 

 out any reference to inevitable differences in the size and con- 

 tours of the different areas or in any other features of the 

 environments ; and that the divergence in the habits may be 

 directly due to the prevention of interbreeding between sep- 

 arated portions which inevitably differ in average character, 

 especially if they are very small portions. 



Isolated portions differ in varying degrees from the average 

 character of the Species. 



The italicized portion of the passage last quoted attributes 

 to isolation, in stronger language than I should be willing to 

 use, a direct influence in producing divergence in the adjust- 

 ments on which fertility in the different portions of the species 

 depend. I should prefer to say that in some species the ad- 

 justments on which fertility depends are so delicate that, 

 adjustments producing perfect fertility within one intergener- 

 ating portion of the species, will not produce fertility in another 

 portion that has been long isolated. I do not make my state- 

 ments so sweeping as his concerning the divergent influence 

 of isolation on any one class of characters, but I include all 

 classes of inheritable characters, in sexually producing organ- 

 isms, as coming under its influence. I also insist that the 

 direct influence of isolation in producing divergence is in pro- 

 portion to the degree of segregation, which varies immensely 

 in different forms of isolation which are equally complete as 

 preventives of intercrossing. A very stable and homogeneous 

 species may be divided by geological subsidence into two large 

 sections, each represented by a vast number of individuals. 

 In such a case the difference in the average character, and con- 

 sequently the degree of segregation, of the two sections will 

 be iniinitesimally small, and the influence of the isolation thus 

 produced will chiefly consist in its preserving in the different 

 sections any diversities that may arise in the effects of natural 

 selection, or of other principles of transformation. The isola- 

 tion between the land animals of Ireland and Britain, which 

 Mr. Wallace cites as adverse to my theory, is of this kind. 

 Again, there may be transportation and isolation of very small 

 fragments of a very variable species. In such a case separa- 

 tion may involve a degree of segregation that from the first 

 produces perceptible divergence. Again, the process by which 



