12 THE NEWEST THEORIES CONCERNING EVOLUTION SEC. 



that it cannot be something altogether different from other 

 parts of the organism. 



When Weismann further expresses the opinion that 

 sexual differentiation itself finds its explanation in his theory 

 alone, he is to be met with the fact that such an explanation 

 is certainly afforded by (1) the importance of preventing in- 

 and-in breeding ; (2) the importance of division of labour. 



Weismann's argument against the inheritance of acquired 

 characters seems to me to be abandoned by himself in his 

 acknowledgment of the inheritance of the tendencies (pre- 

 dispositions) to new characters acquired during life. In an 

 article on this question 1 I have remarked that any such 

 tendency certainly implies a corresponding molecular 

 peculiarity of the germ-plasm. 



"Let us assume," I said, "that all living beings have 

 evolved one out of another, then, on the basis of Weismann's 

 conception itself, it must be acknowledged that the predis- 

 position to the acquisition of characters, and with that the 

 molecular structure of the germ-plasm, has in the course of 

 time experienced great changes ; even with predispositions 

 it is a question of characters acquired in the course of time 

 and inherited." 



Further, Weismann grants a slight degree of inheritable 

 external influence on the germ-plasm. 



The greatest stress, however, is laid by him on the fact that 

 no inheritance of injuries incurred during life has been 

 proved. 



That injuries incurred during life are but seldom trans- 

 mitted to the offspring does not appear to me wonderful : 

 the inheritance of the complete form and complete activities 

 of the organism, which took root such enormously long 

 periods of time ago, and has been strengthened at each 

 generation, will as a rule counterbalance in the offspring any 



1 Deutsche Litteraturzettung, 15th May 1886. 



