316 Action of the Genetic Material 



discusses this point and comes to conclusions which fit the genetic 

 facts much better, part of which were anticipated in our discussion of 

 Brachet's work. 



Weiss argues in the following way: while it is conceivable that 

 differentiation resides in discrete particles, we cannot be sure that the 

 synthesis of the specific macromolecular compounds which make up 

 these cytoplasmic particles actually takes place in the location where 

 they are found (self-duplication). This would imply that growth 

 occurs in innumerable centers throughout the cytoplasm. On the 

 contrary, in the growth of the neurone Weiss showed that protein 

 synthesis takes place near the nucleus, as Caspersson assumed. There- 

 fore, Weiss believes that the basic protoplasmic units are reproduced 

 within the nuclear space in a complex primordial form determined 

 by the whole genie apparatus. (We would say by the non-genic part 

 of the chromosomes; see, above, our discussion on trophochromatin.) 

 They would be alike for all cells of a given individual of a given 

 species. Upon being released into the cytoplasm, they would be 

 subject to conversions and modifications. To quote Weiss, "Especially, 

 upon impact with certain specifically shaped template systems, they 

 would assume conforming shapes and thus perpetuate particular 

 molecular patterns." According to Weiss, each cell strain develops 

 during differentiation its ovm specific population of template molecules 

 (which is his way of describing stratification — chemodifferentiation in 

 terms of molecules ) and, therefore, the same primary nuclear products 

 will assume different types according to the particular molecular 

 populations with which they make contact. "According to this concept, 

 differentiated protoplasmic units would owe their origin and their 

 specific shapes to two entirely different processes, occurring in different 

 places. They would be propagated in the nuclear center and be 

 remodeled in the cytoplasm" (Weiss). What appears to be seff- 

 reproducing bodies in the cytoplasm are "model centers of adsorption, 

 aggregation, alignment, and conversion of compounds which have 

 originated in a distant location." 



I have no doubt that this way of looking at growth and dff- 

 ferentiation is, in principle, far superior to that of the autonomous 

 cytoplasmic particles, and also in much better accord with basic 

 genetic ideas, as has been shown. The geneticist can easily conceive 

 of growth and differentiation being basically separate processes, and 

 has done so ( Goldschmidt, 1927, 1938a). As we have seen, many facts 

 point to growth, as such, being controlled by the non-specific (i.e., 

 non-genic) parts of the chromosomes. This does not mean that growth 



