312 THE GERM-PLASM 



germ-cell which will give rise to the father, and still may not 

 result in the production of the type of the grandfather ; and that 

 these may then pass into a germ-cell of the next generation, 

 and partially determine the type of the son, provided that they 

 are opposed to a group of idants which has a weaker controlling 

 force. At every ontogenetic stage, then, the struggle of the ids 

 and idants decides which group of the latter is to control the 

 cell. According to the hypothetical principle on which we have 

 supposed this struggle to take place, the majority of homodyna- 

 mous determinants would always represent the greatest con- 

 trolling force, so that certain of the more comprehensive or 

 special characters of the grandparent might very well reappear 

 in the grandchild, even if only six or eight idants which con- 

 trolled the development of the grandparent were present in the 

 germ-plasm from which the grandchild arises. 



We may even assume that, as regards Man, ontogeny is hardly 

 ever passed through without reversions occurring to one or other 

 of the grandparents ; for determinants of one of the grand- 

 parents will almost invariably have been suppressed in the 

 development of the parent by stronger ones derived from the 

 germ-cell of the other grandparent, and will predominate in 

 the formation of the grandchild, because they are here again 

 opposed to other combinations of ids over which they may pre- 

 ponderate under certain circumstances. It may therefore happen 

 that some of the individual characters of the grandparent may 

 reappear in the grandchild, although there may be no general 

 resemblance between the two. 



The answer to the above question relating to the causes on 

 which reversion to a grandparent depend, may be briefly stated 

 as follows : — such a reversion is due to the fact that the whole or 

 pa?'t of the group of idants which determine the type of the 

 grandparent were present in that germ-cell of the parent from 

 which the grandchild was developed, and that it was there 

 opposed to a weaker group derived fro7n the other parent. 



We do not know what number of the controlling idants of the 

 grandparent must be present in the germ-plasm of the grand- 

 child in order that reversion to the grandparent may occur. 

 Complete reversion can only take place if none of the deter- 

 mining idants are absent ; but, as w'e have seen, such complete 

 reversion has not by any means been proved to occur in Man. 

 Still less is this the case in the next following generation^ viz... 



