and we resume our inquiry 43 



called the psychological or mnemic theory 

 of heredity. Obviously we must begin from 

 the biological side, for we have no dire^ 

 experience in the matter. Moreover it is 

 not our memory, but a so-called organic 

 memory with which we are concerned. 



Now if it is once admitted that the body 

 influences the germ-plasm in one way — i.e. 

 by way of nutrition — the possibility of its 

 influence in other ways can hardly be denied. 

 Even the influence in the one way may mean 

 a great deal more than Weismann surmised, 

 may involve not merely quantitative differ- 

 ences but qualitative differences as well. 

 Truly, as Mephistopheles said: "Blut ist ein 

 ganz besondrer Saft" For example, through 

 the blood there circulate certain secretions, 

 called hormones, destined— as our Regius 

 Professor of Medicine has said— "for the 



