138 ARE THE EFFECTS OF USE INHERITED? 



is the hypothesis of Pangenesis, according to 

 which each modified cell, or physiological unit, 

 throws off similarly-modified gemmules or parts 

 of itself, which ultimately reproduce the change 

 in offspring? If we reject pangenesis, it becomes 

 difficult to see how use-inheritance can be 

 possible. 



PANGENESIS IMPROBABLE. 



The more important and best-known phe- 

 nomena of heredity do not require any such 

 hypothesis, and leading facts (such as atavism, 

 transmission of lost parts, and the general non- 

 transmission of acquired characters) are so adverse 

 to it that Darwin has to concede that many of the 

 reproductive gemmules are atavistic, and that by 

 continuous self-multiplication they may preserve 

 a practical " continuity of germ-substance," as 

 Weismann would term it. The idea that the 



