WEISMANN'S THEORY 139 



j>arts, cells, parts of cells, groups of cells and other 

 concrete structures. The biophors represent charac- 

 ters, and a germ cell contains as many biophors as 

 the individual which this cell is to create Mall possess 

 elementary indivisible characters, for complex char- 

 acters result from various combinations of elementary 

 characters. Every biophor may vary independently 

 so as to produce a corresponding modification in the 

 character it represents and determines; every biophor 

 can assimilate, grow and multiply by division. 



The germ plasm is not a mere loose aggregate of 

 determinants; it possesses a structure, an architec- 

 ture, in which the individual determinants have each 

 their definite location. This location cannot be deter- 

 mined by chance but depends partly on their historical 

 development from earlier ancestral determinants, and 

 partly on internal forces called "vital affinities" to dis- 

 tinguish them from "chemical affinities." 



What happens then when the ovum undergoes 

 cleavage and development begins? As every deter- 

 minant in the ovum stands in a certain relation to other 

 determinants as to location, the process of develop- 

 ment must be such that one determinant reaches 

 through innumerable cellular divisions the very cell 

 which it is to determine. This would be impossible 

 unless there were qualitative differences in the first 

 two sister-cells which appear after the cleavage of the 

 ovum. One may contain, for instance, all the deter- 



