22 THE BIOLOGICAL PROBLEM OF TO-DAY 



Naegeli) lies not in the general protoplasm of the 

 ovum and spermatozoon, but in their nuclear 

 matter (hypothesis of Hertwig and Strasburger). 

 Weismann calls this the germ plasm, so altering 

 the previous connotation of the word. The germ- 

 plasm of every species has an extremely compli- 

 cated, stable architecture, an architecture that has 

 been elaborated gradually in the course of past 

 time. In this he distinguishes simple and complex 

 component parts, the biophores, determinants, ids, 

 and idants. 



The biophores are his smallest material units, 

 and to them are due the fundamental qualities of 

 life assimilation, metabolism, and reproduction by 

 division. Thus, they correspond to Herbert Spencer's 

 physiological units, Darwin's gemmules, De Yries' 

 pangenes, and Hertwig's idioblasts. They are the 

 bearers of the various characters of cells, and there 

 are present in the germplasm a very large multitude 

 of different kinds of them, corresponding to the 

 number of cells with different characters. 



The determinants are units of the rank next 

 higher ; they have qualities of their own, but are 

 composed of groups of several kinds of biophores. 

 They, too, have the power of division which is 

 associated with, and comes about by, multiplication 

 of the coherent company of biophores which lies 

 within them. 



The histological character of every cell in a 

 multicellular organism is determined by a single 

 determinant (cell-determinants). Weismann has 

 framed his conception of determinants so as to 



