MECHANISM AND HEREDITY 57 



indefinite extent and yet retaining its original 

 structure. 



We might, perhaps, get over the difficulty 

 for a generation or two of cells, by assuming 

 that the germ-plasm contains, not one, but 

 several nuclear mechanisms, and that only 

 one of these mechanisms comes into play at 

 each reproduction, others being left to form 

 the germ-plasm of the next generation, or 

 otherwise to provide for emergencies. As a 

 matter of fact, a theory of this kind has been 

 put forward in order to account for the fact 

 that, as has been shown so clearly by Driesch 

 and others, not only the germ-cells, but also 

 other cells in the developing embryo, or even 

 in the adult organism, may, on occasion, give 

 rise to the reproduction of a whole organism. 

 It has been supposed that parts of the original 

 germ -plasm, or, in plain English, nuclear 

 mechanisms capable of giving rise to the re 

 production of a whole organism, may and do 

 pass into ordinary somatic cells, as well as into 

 the direct line of future sexual reproductive 

 cells. 



This far-fetched hypothesis only makes 

 matters worse for the mechanistic theory of 



