76 THE GERM-PLASM THEORY 



subsequently to form the butterfly. Moreover, 

 both sets must have existed side by side in the 

 egg. Then there are the reserve determinants 

 which will be mentioned in connexion with the 

 question of regeneration. And, finally, we even 

 hear of " highly developed musical determinants, 

 which we must assume in the case of musical 

 genius " (Vol. ii. 149). 



Smaller even than the determinants are the 

 " biophors," which are the vital units of the germ, 

 and may be looked upon as separate living things, 

 so to speak, existing in that microcosm the germ- 

 cell ; units " which feed and reproduce, which 

 assimilate and which bear a charm against the 

 assimilating power of the surrounding proto- 

 plasm " (i. 401). 



In some shape or another such vital units have 

 been thought of by many scientific writers, since 

 we have the " physiological units " of Herbert 

 Spencer, the " gemmules " of Darwin, the " idio- 

 blasts " of Hertwig, the " micellae " of Nageli, 

 and the " pangenes " of de Vries. These vital units 

 are the bearers of the characters of cells in the 

 adult organism. 



Perhaps it is well to pause at this moment, and 

 to remind the reader that all these things just 

 named and described are pure assumptions, not 

 one of them being demonstrable by the micro- 

 scope, unless indeed an " idant " may be the same 

 as a single thread of chromatin, which is an un- 

 proved and probably unprovable assumption. It 

 is necessary to insist upon this because, when read- 

 ing the book, one is apt to be so much carried 



