THE CELLULAR BASIS 101 



tinuity and somatic discontinuity of successive 

 generations. 



Thus the problem which faces the student 

 of heredity and development has been cut in 

 two; he no longer inquires how the body pro- 

 duces the germ cells, for this does not happen, 

 but merely how the latter produce the body 

 and other germ cells. The germ is the unde- 

 veloped organism which forms the bond be- 

 tween successive generations; the body is the 

 developed organism which arises from the 

 germ under the influence of environmental 

 conditions. The body develops and dies in 

 each generation ; the germ-plasm is the contin- 

 uous stream of living substance which con- 

 nects all generations. The body nourishes 

 and protects the germ; it is the carrier of the 

 germ-plasm, the mortal trustee of an immortal 

 substance. 



This contrast between the germ and the 

 body, between the undeveloped and the devel- 

 oped organism, is fundamental in all modem 

 studies of heredity. It was especially empha- 

 sized by Weismann in his germ-plasm theory 

 and recently it has been made prominent by 



