260 HEREDITY AND ENVIRONMENT 



cal substances which preserve their individu- 

 ality in various combinations, just as groups 

 of atoms or radicals do in chemical reactions; 

 they may be dropped out or added, substituted 

 or transposed, just as chemical radicals may 

 be in chemical compounds. To this extent 

 they maintain continuity and independence, 

 but they are not absolutely independent for 

 they react upon one another as well as to en- 

 vironmental changes, so that the characters of 

 the developed organism are the results of all 

 these reactions and interactions. 



Inheritance Factors and Germinal Units 



If it is asked whether there are particular 

 structures in germ cells which correspond to 

 particular inheritance factors it must be ad- 

 mitted that we have no certain knowledge on 

 this subject and that opinions differ greatly 

 with respect to it. On the one hand it is 

 maintained that the entire germ is concerned 

 in the development of every character, and on 

 the other hand that the differential cause of 

 any character may be located in some differ- 

 entiated structure or function of the germ. 



