THEOUGH CUMULATIVE SEGEEGATION. 



205 



" will generally lead to the most different or divergent varia- 

 tions being preserved and accumulated by natural selection." 

 Now it cannot be doubted that ability to appropriate unused 

 resources would be an advantage to any members of a com- 

 munity pressed for food ; but I do not see how the divergence 

 that would enable them to appropriate, for example, a new kind 

 of food can be accumulated while free crossing continues ; and 

 Natural Selection cannot prevent the free crossing of competitors 

 who leave progeny. 



Having found that the evolution of the fitted is secured 

 through the prevention of crossing between the better fitted 

 and the less fitted, can we believe that the evolution of a 

 special race, regularly transmitting a special kind of fitness, 

 can be realized without any prevention of crossing with other 

 races that have no power to transmit that special kind of 

 fitness ? Can we suppose that any advantage, derived from 

 new powers that prevent severe competition with kindred, can 

 be permanently transmitted through succeeding generations to 

 one small section of the species while there is free crossing 

 equally distributed between all the families of tlie species ? Is 

 it not apparent that the terms of this supposition are inconsis- 

 tent with the fundamental laws of heredity ? Does not inheri- 

 tance follow the lines of consanguinity ; and when consanguinity 

 is widely diffused, can inheritance be closely limited ? When 

 there is free crossing between the families of one species will not 

 any peculiarity that appears in one family either be neutralized 

 by crosses with families possessing the opposite quality, or being 

 preserved by natural selection, while the opposite quality is 

 gradually excluded, will not the new quality gradually extend to 

 all the branches of the species ; so that, in this way or in that, 

 increasing divergence of form will be prevented ? 



If the advantage of freedom from competition in any given 

 variation depends on the possession, in some degree, of new 

 adaptations to unappropriated resources, there must be some 

 cause that favours the breeding together of those thus specially 

 endowed, and interferes in some degree with their crossing with 

 other variations, or, failing of this, the special advantage will in 

 succeeding generations be lost. As some degree of Independent 

 Generation is necessary for the continuance of the advantage, it 

 is evident that the same condition is necessary for the accumu- 

 lation through Natural Selection of the powers on which the 



LINN. JOTJBN. — ZOOLOGY, VOL. XX. 17 



