THROUGH CUMULATIVE SEGREGATION. 



223 



followed without separating those differently endowed, we shall 

 have, in the very nature of such variation, a cause of segregation 

 and of divergent evolution. Some slight variation in the di- 

 gestive powers of a few individuals makes it possible for them to 

 live exclusively on some abundant form of food, which the species 

 has heretofore only occasionally tasted. In the pressure for 

 food that arises in a crowded community these take up their 

 permanent abode where the new form of food is most accessible, 

 and thus separate themselves from the original form of the 

 species. These similarly endowed forms will therefore breed 

 together, and the offspring will, according to the law of Diver- 

 gence through Segregation, be still better adapted to the new 

 form of food. And this increasing adaptation, with increasing 

 divergence, might continue for many generations, though every 

 individual should come to maturity and propagate ; that is, though 

 there were no enhancing of the effect through Diversity of 

 Selection, or indeed through any other cause producing Intensive 

 Segregation. And when different forms of Intension do arise, 

 they may be entirely independent of change in the environment, 

 the only change being in the forms or functions of the organism. 



In choosing a name for this form of Segregation I first thought 

 of calling it Physiological or functional Segregation. But such 

 a name is, on closer examination, found to imply both too much 

 and too little ; for on the one hand there is probably no form of 

 segregation that is not in some way or in some degree due to 

 physiological or functional causes, and on the other hand this 

 special form of segregation is as dependent on psychological 

 causes which guide the organism in finding and in adhering to 

 the situation for which it is best fitted, as it is on the initial 

 divergence of the more strictly physiological adaptations by 

 which it is able to appropriate and assimilate the peculiar form 

 of resource. In the case of freely moving animals, the psycho- 

 logical guidance is an essential factor in the success of the in- 

 dividual ; while in the case of plants and low types of animal life, 

 the suitable situation is reached by a wide distribution of a vast 

 number of seeds, spores, or germs, and the same situation is 

 maintained by a loss of migrational power as soon as the germs 

 begin to develop. In these lower organisms it is evident that 

 the success of the individual must depend on its physiological 

 rather than on its psychological adaptations ; and if an initial 

 divergence of adaptations results in a slight difference in the kinds 



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