96 ANALYSIS OF THE FOUR PRINCIPLES. 



the pure unions, which may, therefore, be called segregate survival. 

 Segregate union and segregate survival are forms of negative segrega- 

 tion ; for without the aid of other influences they can not bring the 

 compatible individuals into relations producing pure unions. 



Segregate union includes dimensional, structural, and potential 

 segregation, and it is of no small interest to note that the free and 

 abundant distribution of the fertilizing elements of the different types, 

 when cooperating with any one of these, secures conditions necessary 

 for pure unions. This cooperation, therefore, produces positive segre- 

 gation as truly as do sexual and social instincts that bring together 

 those of one race. 



(2) Physiological selection is so defined and described by Romanes 

 as to include three of these eight forms of impregnational segregation. 

 The three forms thus grouped are potential segregation, segregate 

 fecundity, and segregate vigor. In his last book he uses "physiolog- 

 ical isolation ' ' to cover the same principles wherever they occur, re- 

 serving physiological selection for cases concerned in the origination 

 of specific types.* I greatly prefer the term physiological isolation to 

 physiological selection, for it seems to me that selection should be 

 used for the superior success of forms that are both competing and 

 freely intergenerating, and not to designate isolative principles. 



(3) Four classes of self-cumulative endowments. Before discussing 

 these principles of negative segregation, through which the influence 

 of positive segregation is greatly increased, it will be an advantage 

 if we can gain some idea of the nature of cumulative fertility in its 

 relations to a law of still wider import. I refer to the fourfold law of 

 antagonistic increase and mutual limitation between (i) integration, 

 (2) segregation, (3) adaptation, (4) multiplication in other words, be- 

 tween (i) general invigoration and power of variation through cross- 

 ing; (2) opening of new opportunities and independent possibilities 

 through segregation; (3) special adaptation to present circumstances; 

 (4) powers of multiplied individualization. Darwin has considered at 

 length the first and the third, though I do not remember that he has 

 anywhere pointed out that their development is due to a kind of 

 self- augmentation. I believe this is so emphatically the case that the 

 former might well be called the law of self-cumulative vigor and the 

 latter the law of self-cumulative adaptation. Corresponding to these 

 two laws I find the additional laws of self-cumulative segregation and 

 self-cumulative fertility. Darwin's theory that diversity of natural 

 selection is directly and necessarily dependent on exposure to different 



* See Darwin and After Darwin, Part III, p. 9. 



