J. T. Gulick — Inconsistencies of Utilitarianism. 7 



there can be no change, either of habits or structure, when 

 portions of the same species are isolated in different areas 

 under the same environment, appears from the statement on p. 

 149, that — " If the average characters of the species are the 

 expression of its exact adaptation to its whole environment, 

 then, given a precisely similar environment, and the isolated 

 portion will inevitably be brought back to the same average of 

 characters." And this he maintains will be the case even " if 

 we admit, that, when one portion of a species is separated 

 from the rest there will necessarily be a slight difference in the 

 average character of the two portions." 



-Does the Difference in the Environment increase with each suc- 

 cessive Mile f 



If the divergences presented by the Sandwich Island land 

 molluscs are wholly clue to exposure to different environments, 

 as Mr. Wallace argues on pages 147-150, then, there must be 

 completely occult influences in the environment that vary pro- 

 gressively with each successive mile. This is so violent an 

 assumption that it throws doubt on any theory that requires 

 such support. Of all the suggestions made by Mr. Wallace 

 concerning possible and inevitable differences in the environ- 

 ments presented in the successive valleys, it seems to me not 

 one meets the requirements of the case, or throws any light on 

 'the subject. The one suggestion which is quite applicable as 

 an explanation is the one already quoted that " the isolated 

 portion is at once in a different position as regards its own 

 kind." This is, I believe, a most potent difference, which (as 

 Mr. Wallace's language seems to indicate), is directly intro- 

 duced by isolation, and (adhering to the meaning usually 

 given to environment,) is not at all due to difference in the 

 environments presented in the different areas. 



Unstable Adjustments disturbed by Isolation. 



There is a sentence in another chapter of Mr. Wallace's 

 book which attributes to isolation (though without recogniz- 

 ing the important results that must follow) just that kind of 

 influence in introducing a certain class of physiological diver- 

 gences, which I claim for it in introducing, not only physio- 

 logical, but also psychological and morphological divergences. 

 I claim that there is, in many species, more or less variation 

 with unstable adjustment, in the habits which determine what 

 forms of food it shall appropriate, and that, when a few indi- 

 viduals of such a species (the offspring perhaps of a single 

 female) are isolated, this adjustment is often so disturbed by 



