Reprinted for private circulation from 



The Botanical Gazette, Vol. LXX, No. 6, December 1920 



-V YQlff 



botani, 



ORIGIN OF MECHANISM OF HEREDITY 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 274 



Merle C. Coulter 



The gross features of the mechanism of heredity have become 

 features of general knowledge. The majority of biologists think 

 of heredity in terms of determiners located upon the chromosomes. 

 There are certain critical details of the mechanism, however, 

 which still remain profoundly obscure. Little is known of the 

 exact nature of the determiners themselves. The orderliness in 

 the behavior of the determiners, that is, how they are "released" 

 to express themselves only at the appropriate moments in the life 

 history of the organism, seems not to have been clearly visualized. 

 Finally, the possible origin of this mechanism of heredity is seldom 

 even discussed. The present paper suggests, although only in a 

 very brief and general way, certain answers to these questions. 



It seems safe to assume that the most primitive organism 

 lacked not only an organized nucleus, but even the components 

 of a nucleus. A consideration of the activities of such an organism 

 will reveal a suggestion as to the origin of the hereditary mechan- 

 ism, provided, of course, that the assumptions are sound. The 

 metabolism of this primitive organism, in certain fundamental 

 features, will be similar to that of all organisms. Raw materials 

 will be taken in and transformed to provide building materials 

 and energy. If the raw materials be pure and the machinery of 

 the protoplast perfect, this transformation will be complete, so 

 that all the raw materials taken in will be transformed and used. 

 Actually, however, the raw materials provided are never quite 

 pure, and the machinery of the protoplast, although infinitely 

 more efficient than any man-made machine, must be subject to 

 certain flaws and frictions of its own. The transformation and 

 use of materials, therefore, will not be complete; certain waste 

 materials and by-products will remain. We are not concerned 



^with the waste material; it is the fate of the by-products which is 



•— significant. 



459] [Botanical Gazette, vol. 70 



