WEISMANN'S THEORY 141 



which determine the cell's specific characters) and 

 some other passive (those which, for the time being, 

 exert no influence and will not exert any until a later 

 time) . The active ones only break up into biophors. 



Regarding the process by which biophors determine 

 the various characters in the cells which they penetrate, 

 Weismann states that it is not necessary for the bio- 

 phors to be endowed, like De Vries' pangenes, with 

 the very properties which impart to a cell for in- 

 stance the character of a muscle cell or of a nerve cell. 

 Through its action upon the elements of the cellular 

 body, a specific biophor of the muscle substance cre- 

 ates this substance whenever it penetrates the appro- 

 priate cell-body, even though it may not be a contrac- 

 tile element itself. The biophors may transform the 

 general character of an unspecialised embryonic cell 

 into the specific cell of a certain tissue but they do not 

 themselves possess any specific histological characters 

 and cannot effect that transformation without the 

 co-operation of the cell-body. In fact the biophor 

 is not a character bearer, but a factor, in the algebraic 

 sense of the word, the other factor being the cyto- 

 plasm of the cell. 



It is evident that the determinants liberated in the 

 course of the embryonic development cannot be re- 

 covered by the cell which released them. How can 

 then the adult organism possess sexual products, every 

 cell of which contains every category of determinant 



