84 THE BIOLOGICAL PROBLEM OF TO-DA Y 



isms, immortal germplasm, and mortal somatic 

 cells, is a misconception. For the continuity of 

 the process of development, or the mode of trans- 

 formation of organic material, depends upon the 

 continual formation and eventual destruction of 

 newly-formed material, but in no way implies the 

 continuous existence of the organised material in a 

 state of organisation. From this point of view, the 

 immortality of unicellular organisms and of the 

 germplasm breaks down, and, above all, the artificial 

 distinction between somatic cells and reproductive 

 cells. For, in the latter, the organic process of 

 development, with its transformation of organic 

 material, also occurs. 



Here I may give the conclusion of this division 

 of my argument. Cells multiply only by doubling 

 division. Between somatic cells and reproductive 

 cells there is no strong contrast, no gulf that cannot 

 be bridged. The continuity of the process of 

 development depends upon the power of the cells 

 to grow and to divide, and has already been set 

 forth in the sayings Omniscellulaecellida, omnis 

 nucleus e nucleo. Whatever novelty the doctrine 

 of the continuity of the germplasm brings into this 

 saying depends upon error, and is in contradiction 

 to known natural facts. 



II. ARGUMENTS AGAIN ST THE DOCTRINE OF 

 DETERMINANTS. 



Weismann has united his doctrine of determinants 

 with his assumption of a differentiating division. 

 He conceives that every little group of cells in the 



