TRANSMISSIBILITY OF FUNCTIONAL MODIFICATIONS 107 



certainly come under the category ot" functional modifications, and 

 it might be thought that we have here a case of transmission of such 

 an acquired character. 



Against this, however, we have to put the fact that tlte acquired 

 immunity is not transmitted from the father to the descendants. 

 Hertwig attempts to explain this by saying that the short duration 

 of the experiments has only allowed the poison to aftect the cell- 

 substance (cytoplasm) and not the nucleus, that is, the hereditary 

 substance of the sperm-cells, an assumption which has little proba- 

 bility considering the intimate nutritive relations between the cell- 

 nucleus and the cytoplasm. I should be rather inclined to conclude 

 from the difference in the transmitting power of the sperm and of 

 the ovum, that this ' inheritance of immunity ' does not depend, as 

 Hertwig supposes, on a modification of the cells to ' ricin immunity,' 

 but, as Ehrlich and the bacteriologists believe, on the production of 

 so-called ' anti-toxins,' and that these anti-toxins are handed on to 

 the embryo not by the ovum itself, but by the interchange of blood 

 between mother and offspring which lasts throughout the whole 

 embryonic period. It is then self-evident why no transmission of 

 immunity through the father occurs. 



But it would lead me too far were I to attempt to refute all 

 the attempts that have been made to interpret individual cases as 

 due to the inheritance of acquired characters. I should, however, 

 like to say something as to the theoretical possibility of such an 

 assumption. 



When we try to conceive how experiences and their consequences 

 can be entailed, how new acquirements of the ' personal part can have 

 representative effects on the germinal part,' we find ourselves con- 

 fronted with almost, if not entirely, insuperable difficulties. How 

 could it happen that the constant exercise of memory throughout 

 a lifetime, as, for instance, in the case of an actor, could influence 

 the germ-cells in such a way that in the offspring the same brain- 

 cells which preside over memory will likewise be more highly 

 developed — that is, capable of greater functional activity 1 We know 

 what Zehnder's answer to such a question would be ; he would make 

 the blood the intermediary between the brain-cells and the germ-cells, 

 but we have seen that specific food-stufis for each specific cell-group 

 cannot be assumed, and that, even if they could, they would not 

 meet the necessities of the case. Yet every one who does not regard 

 the germ-plasm as composed of determinants is constrained to make 

 some such assumption. But if we take our stand upon the theory 

 of determinants, it would be necessary to a transmission of acquired 



