Earlier Theories of Heredity 13 



the theory of germinal selection. In the first place 

 he imagined that each id is composed of determinants, 

 which are ultra-microscopic, each of them representing, 

 not the whole body structure as does an id, but all the 

 characters that belong to a particular kind of cell. 

 Each determinant in turn was conceived of as composed 

 of still smaller units called biophores, each of which 

 represented a single character of a cell. Biophores 

 have the capacity to assimilate food, to grow, and to 

 reproduce themselves in the germ plasm. This imagi- 

 nary structure of the cell is spoken of as Weismann's 

 cell architecture, in which biophores are built into deter- 

 minants, determinants into ids, ids into idants. In 

 fact, this is a remarkable theoretical analysis of the 

 structure of a chromosome. 



Selection is conceived of as occurring in the following 

 way. After fertiUzation the biophores are too numerous 

 for all of them to obtain expression, and the result is 

 a struggle for existence, a sort of ultra-microscopical 

 warfare. As a consequence some biophores perish and 

 others survive and are perpetuated. This struggle of the 

 biophores for nutrition, and the almost infinite combina- 

 tions that might enter into the structure of the resulting 

 determinants, would open up a wide field for variation. 

 This is the theory of germinal selection, a struggle and 

 a survival of fortunate biophores, and it may well 

 be regarded as fantastic. It has been discarded, not 

 only because it is without foundation in fact, but 

 chiefly because it is beyond the reach of experimental 

 testing. 



What is called Weismannism had a very wide influ- 

 ence for a number of years, and the continuity of the 



