WEISMANN'S THEORY OF THE GERMPLASM 23 



avoid the supposition that every single cell is 

 represented in the germplasm by its own biophores. 

 There are small parts in the body in which the 

 cells are all alike, and for these parts a single 

 determinant suffices, afterwards multiplying by 

 division. On the other hand, each cell or cell- 

 group in the body, that is independently variable, 

 must have its special determinant in the germ- 

 plasm. And so the germplasm of a species must 

 possess as many determinants, or guiding par- 

 ticles, as there are in the organism cells or cell- 

 groups that are independently variable in the 

 germ or in later stages (hereditary pieces or deter- 

 minates). 



As every cell or group of cells which corresponds 

 to determinants has a definite position in the body, 

 Weismann infers that the determinants are defi- 

 nitely placed in the germplasm, and form an ordered, 

 complicated community. He has given the name 

 id to these communities, which are higher units 

 with definite constitution and with complicated 

 architecture. These ids are bodies containing all 

 the determinants necessary to build up the indi- 

 vidual of a species, and correspond to what Weis- 

 mann previously called ancestral plasms. Every 

 id must be able to grow and multiply, for it is by 

 their multiplication that the germplasm for new 

 individuals is formed. 



A single id would suffice for the conduct of a 

 single life - history ; Weismann, however, in the 

 pursuit of a chain of thought connected with the 

 relation of sexual reproduction to heredity, and 



