ASPECTS OF KINETIC EVOLUTION 327 



Organic energy is primarily an integration of cellular energy, 

 and the energy of cellular development has to be readjusted 

 and renewed by conjugations between cells of diverse descent. 

 The answer to the question why this is so must come from a 

 new department of science, a general cellular biology which 

 shall study the problems of cellular organization and associa- 

 tion. It is here, if anywhere, that we must learn why organisms 

 are normally diverse, why interbreeding is necessary and why 

 evolution follows as a universal consequence. A species, 

 viewed as a protoplasmic fabric of interwoven lines of descent, 

 is different from any other object in nature, but its properties 

 and potentialities are no less peculiar than its structure and its 

 modes of motion. 



5. THE HEREDITY CONCEPT MODIFIED BY HETERISM. 



Questions are debated with the most persistence and the least 

 profit when diverse opinions are being expressed by means of 

 the same words. The term heredity has figured largely in evo- 

 lutionary discussions ever since the time of Darwin, and yet the 

 ideas which it represents are by no means the same in the minds 

 of the many investigators who use it. The meanings do not 

 vary merely in the extent of their application to related ideas. 

 They differ fundamentally in their standpoints, and in their 

 conceptions of the nature of the causes of evolution. 



The traditional concept of heredity, the supposed production 

 of like by like, also enters largely into the composition of the 

 various philosophical systems of evolution, so largely, in fact, 

 that evolution, descent and heredity are often treated as synony- 

 mous terms. Indeed, the whole subject of evolution is often 

 summarized and crystallized into heredity, so that no further 

 thinking is possible which does not definitely adopt or as defi- 

 nitely reject the heredity conceptions of the various schools of 

 evolutionary study. The extreme views are very widely diver- 

 gent, and perhaps equally remote from the truth. 



On the one side is the hypothesis of environmental causation, 

 or a direct impression or moulding of characters by external 

 conditions ; on the other side is the hypothesis of prefiguration 

 or definite predetermination of characters by internal character- 



Proc. Wash. Acad. Sci., February, 1907. 



