I06 ON HEREDITY. 



in the latter succession the germ-plasm remains similar, while 

 in the succession of the former it becomes different. Thus 

 individuals, as they arise, are always assuming new and more 

 complex forms, until the interval between the simple uni- 

 cellular protozoon and the most complex of all organisms — 

 man himself^is bridged over. 



I have not been able to throw light upon all sides of the 

 question which we are here discussing. There are still some 

 essential points which I must leave for the present ; and, 

 furthermore, I am not yet in a position to explain satisfactorily 

 all the details which arise at every step of the argument. 

 But it appeared to me to be necessary to state this weighty 

 and fundamental question, and to formulate it concisely and 

 definitely ; for only in this way will it be possible to arrive at 

 a true and lasting solution of the problem. We must however 

 be clear on this point — that the understanding of the pheno- 

 mena of heredity is only possible on the fundamental sup- 

 position of the continuity of the germ-plasm. The value of 

 experiment in relation to this question is somewhat doubtful. 

 A careful collection and arrangement of facts is far more likely 

 to decide whether, and to what extent, the continuity of germ- 

 plasm is reconcilable with the assumption of the transmission 

 of acquired characters from the parent body to the germ, and 

 from the germ to the body of the offspring. At present such 

 transmission is neither proved as a fact, nor has its assumption 

 been shown to be unquestionably necessary. 



