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 codperating with any one of these, secures conditions necessary 
for pure unions. ‘This codperation, 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 selj-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 widerimport. I refer to the fourfold law of 
antagonistic increase and mutual limitation between (1) integration, 
(2) segregation, (3) adaptation, (4) multiplication—in other words, be- 
tween (1) 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. 
