Isolation. 19 



For, in this case, the chances would be infinitely 

 against the average characters of the original half- 

 dozen individuals exactly coinciding with those of 

 all the rest of their species. 



2. In any case of homogamy, however, it is 

 immaterial wliat proportional number of individuals 

 are isolated in the first instance. For the isolation is 

 here discriminate, or effected by the initial difference 

 of the average qualities themselves— a difference, 

 therefore, which presupposes divergence as having 

 already commenced, and equally bound to proceed 

 whether the number of intergenerants be large or 

 small. 



It may here be remarked that, in his essay on 

 the Influence of Isolation, Professor Weismann fails 

 to distinguish between the two kinds of isolation. 

 This essay deals only with one of the many different 

 forms of isolation — the geographical — and is therefore 

 throughout concerned with a consideration of diversity 

 as arising from apogamy alone. But in dealing with 

 this side of the matter Weismann anticipated both 

 Gulick and myself in pointing out the law of inverse 

 proportion, which I have stated in the preceding 

 paragraph in what appears to me its strictly accurate 

 form. 



3. Segregate Breeding, or homogamy. which arises 

 under any of the many forms of discriminate isolation, 

 must always tend to be cumulative. For, again to 

 quote Mr. Gulick, who has constituted this fact the 

 most prominent as it is the most original feature 

 of his essay, '-In the first place, every new form of 

 Segregation^ that now a[)pears depends on, and is 



^ This term may here be taken as equivalent to Isolation. 



C 2 



