HEREDITY AND EVOLUTION 93 



nal mechanism of heredity everywhere shown by 

 Darwin in his remarkable chapter on pangenesis 

 and attested by many passages in his private let- 

 ters. The other is the now general admission 

 that the mechanism over which Darwin so long 

 pondered is to be sought in the organization of 

 the germ-cells. 



PANGENESIS AND THE PRINCIPLE OF GENETIC 

 CELLULAR CONTINUITY 



Of the original hypothesis of pangenesis I shall 

 say but a few words. Darwin says in one of his 

 letters that he had considered it for upwards of 

 five-and-twenty years. It is easily the most ab- 

 stract and speculative portion of all his writings. 

 It was published against the advice of his trusted 

 friend and counselor, Huxley, who had himself 

 many years earlier written one of the first and 

 ablest reviews of the cell-theory that appeared in 

 our language. Darwin predicted that pangene- 

 sis would be called a mad dream; and on its pub- 

 hcation the hypothesis was, in fact, received for 

 the most part with hostile criticism or scanty ap- 

 preciation. In its original form it has been gen- 

 erally abandoned; though one of its principal 

 postulates, remodeled by De Vries to form the 

 hypothesis of " intracellular pangenesis," is still 

 accepted by some biological thinkers. It is none 

 the less deeply significant that so great and saga- 

 cious a naturalist, one whose Ufe was so largely 

 given to the study of the external aspects of 



