38 THE BIOLOGICAL PROBLEM OF TO-DAY 



ment of the egg- cell and must increase as develop- 

 ment proceeds ; for otherwise the different products 

 of the division of the egg-cell could not give rise to 

 entirely different hereditary tendencies. This is, 

 however, the case/ Weismann represents to him- 

 self that 1 * the changes .of the idioplasm depend on 

 purely internal causes, which lie in the physical 

 nature of the idioplasm. In obedience to these, a 

 division of the nucleus accompanies each qualitative 

 change in the idioplasm, in which process the 

 different qualities are distributed between the two 

 resulting halves of the chromatin rods.' 



I shall proceed to show that this conception in- 

 volves material difficulties and contradictions. It 

 will be found that characters totally contradictory 

 are ascribed to Weismann's idioplasm. On the one 

 hand, it is credited with being a stable substance, 

 possessing a coherent, complicated architecture ; in 

 the form of ancestral plasms it is supposed to be 

 handed on, from one individual to another, un- 

 changed through many generations ; on the other 

 hand there is ascribed to it a labile architecture, 

 that allows a free and perpetual casting loose of 

 rudiments, of such a kind that at each division 

 there is caused a complete rearrangement and un- 

 equal division of these rudiments. In the one case, 

 the inner forces produce a reciprocal, coherent bond 

 between the numerous rudiments ; in the other 

 case, permit change of their position and relations 

 to one another, and this not only once but in 

 orderly, definite fashion, different in each of many 



1 English edition, p. 34. 



