SOME! OF THE FACTS EMPHASIZED. 151 



and degrees of amalgamation are liable to arise. This liability is 

 enhanced in case the fragment indiscriminately separated is small; 

 for there is then a possibility that, in some one of its habitudes or 

 aptitudes, it will differ from the original stock in such a way as to 

 insure its using the environment in a somewhat different manner. It 

 is certain that isolation is a principle tending toward the introduction 

 of diversity not only in the forms of environal selection affecting the 

 species, but also in the forms of reflexive selection, of suetude, and of 

 amalgamation. 



The distinction indicated by discriminate and indiscriminate isola- 

 tion pertains only to the generations when group-formation is being 

 shaped by additions brought in from the parent stock or from other 

 groups, and these are usually the earlier generations of the new groups ; 

 but the influence of this primal shaping will continue through subse- 

 quent generations. 



The action of discriminate survival and of suetude is, however, not 

 at all confined to the earlier stages of group formation. 



5. Amalgamation. 



After a group has been considerably differentiated, combination 

 with other groups is described as amalgamation. 



Amalgamation, or the crossing of races that have been segregated 

 for many generations, is a most effective process for introducing varia- 

 tion ; and, if the contrast is not too great, for adding vigor to the stock. 



6. Some of the Facts Emphasized in this Volume. 



(1) That segregation is the underlying principle throughout the 

 whole process of bionomic evolution. 



(2) That the causes producing and intensifying segregation are quite 

 various, and can not all be included under the term " selection," arid 

 that in seeking the causes of organic evolution we must investigate all 

 the natural causes modifying the action of segregate breeding. 



(3) That some of the most powerful influences in the control of seg- 

 regation are due not to different forms of activity in the environment, 

 but to diversity of activities in the organism, and may, therefore, be 

 classed as forms of autonomic segregation. 



(4) That habitudinal demarcations, through partition, are the 

 initial forms of grouping, which, when intensified by election, produce 

 habitudinal segregations, and that habitudinal segregations are often 

 the controlling factors leading to racial segregations. 



(5) That in reflexive selection (that is, selection produced by the 

 relations of members of a species to each other), the influence of the 

 environment in producing the special result is usually very obscure, 



