3IO THE GERM-PLASM 



C, A being derived from the grandmother, in the development 

 of whom this group dominated. C was derived from the grand- 

 father, and preponderated to such an extent over A that it alone 

 determined the type of the son. Hence A remained latent 

 in the idioplasm of the father, who therefore resembled the 

 grandfather and not the grandmother. If now, that germ-cell 

 of the father, from which the child of the third generation was 

 developed, just happened in the reducing division to receive 

 the group of idants of A only, which remained without influence 

 on the development of the father, but which was dominant in 

 the grandmother, a reversion to the grandmother would then 

 become possible. It would occur when this sperm-cell unites 

 with an egg-cell in which the group of idants D has a much 

 weaker controlling force than A. The child would then resemble 

 neither the paternal nor the maternal type, but would be like his 

 grandmother, for the group of idants A determined the type of 

 the grandmother. 



I nevertheless consider it doubtful w^hether reversion of this 

 kind ever occurs so thoroughly and completely as is conceivable 

 theoretically. The facts are unfortunately by no means so 

 decisive as one could wish. No one, so far as I know, has 

 hitherto attempted to ascertain whether complete reversion to a 

 grandparent ever occurs, and from a theoretical point of view I 

 should consider this to be improbable. Similarity to a grand- 

 parent may undoubtedly often be observed, but it does not 

 therefore by any means follow that a correspondence exists 

 between all, or at any rate the greater majority of individual 

 characters, such as is seen in identical' twins. All the parts 

 of the child and grandparent have never been carefully compared, 

 not to mention the fact that such a comparison has never been 

 made at corresponding ages. Moreover, to use the same ex- 

 ample, only those cases could be utilised in questions of re- 

 version in which the father bears no resemblance to the type 

 of the grandmother. Cases of this kind are, however, not quite 

 reliable, and are certainly not common. 



I am therefore inclined to think that in all these cases we are 

 only concerned with a partial and not a complete reversion 

 to the grandparent, — that is, with the reappearance of a more 

 or less extensive aggregate of characters of the grandparent ; 

 and this is certainly sufficient in many cases to produce what 

 appears to be the type of the latter. More or less extensive 



