METAZOA 95 



diagram (Fig. 34). The hereditary units, which determine the possi- 

 biHties open to the animal, are passed on from generation to generation 

 in the germ cells. In the various types of somatic cells, under the 

 environmental conditions which surround each, are realized and mani- 

 fested such of these possibilities as taken together equip the individual 

 with its characteristic features. 



