244 BEV. J. T. GULICK OTT DITERQENT EYOLUTTOW 



generating forms are at the same time equally successful ; where- 

 fore it is not the success, but the separatenesa of the success, 

 that is due to the segeneration. 



(4) The continuance of the descendants of a group in a special 

 form will depend on its Segregation ; but this is a very different 

 thing from the special success of its descendants. The preser- 

 vation of a special hind of adaptation is never due to natural 

 selection, which is the superior success of the higher degrees of 

 adaptation of every kind. 



(5) The power of migration, or any other power directly related 

 to the environment, may be accumulated by natural selection, 

 and afterward lead to Segregation ; but, according to my method 

 of judging, the continuous advantage of Segregation over Inte- 

 gration can never be shown, for both are equally essential in the 

 economy of nature ; and though one process may at one time 

 predominate over the other, the comparative advantage of Segre- 

 gation, if there be such advantage, cannot be the cause of the 

 preservation of forms endowed with segregative qualities, for 

 they will certainly be preserved as long as they are able to win a 

 bare existence, which is often a lower grade of success than the 

 one from which they are passing. 



(6) According to my view, instead of the accumulation of the 

 Segregative prepotency depending on natural selection, the accu- 

 mulation of divergent forms of natural selection depends on some 

 form of Segregation. 



But if the accumulation of Prepotential Segregation is not due 

 to Natural Selection, how shall we explain it ? It is, I think, 

 due to the fact that those forms that have the most of this 

 character are, through its action, caused to breed together. We 

 have already seen, when considering Seasonal and Sexual Segre- 

 gation, that, if Segregation is directly produced by the instincts 

 or physiological constitution of the organism, there is a tendency 

 toward an increasing manifestation of the character in successive 

 generations. Those that have but a slight degree of Segregate 

 prepotency eventually coalesce, forming one race, while those 

 possessing the same character in a higher degree remain more 

 distinct, and their descendants become still more segregate and 

 still more permanently divergent. As long as the segregate 

 forms are able to maintain vigour and secure fair susteutation, 

 the process continues and the separation becomes more pro- 

 nounced. Of this form of the Law of Cumulative Segregation 



