THE CELLULAR BASIS 95 



the process of development and become embry- 

 onic cells and even germ cells it does not 

 destroy this general principle of germinal con- 

 tinuity and somatic discontinuity. 



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 person is the 

 developed organism which arises from the 

 germ under the influence of environmental 

 conditions. The person develops and dies in 

 each generation ; the germ-plasm is the contin- 

 uous stream of living substance which con- 

 nects all generations. The person nourishes 

 and protects the germ, and in this sense the 

 person is merely the carrier of the germ-plasm, 

 the mortal trustee of an immortal substance. 



This contrast of the germ and the person, 

 of the undeveloped and the developed organ- 

 ism, is fundamental in all modern studies of 

 heredity. It was especially emphasized by 



