SHARE OF THE PARENTS IX BUILDING UP THE OFFSPRING 53 



Upon this struggle between homologous determinants depends 

 the possibility of the entire suppression or inhibition of the influence 

 of one parent, the whole diversity in the mingling of paternal and 

 maternal character in the body of the offspring. It is in this 

 that we must seek the explanation of tlie fact that not only whole 

 bodily parts of the child, such as arms, legs, the nature of the skin, 

 the form of the skull, may take after sometimes the father, sometimes 

 the mother wholly or predominantly, but that the small separate sub- 

 divisions of a complex organ may sometimes turn out more maternal, 

 sometimes more paternal. Thus intelligence from the mother and 

 will from the father, musical talent from the father and a talent 

 for drawing from the mother, may be inherited by the same child. 

 I do not doubt that genius depends in great part on a happy 

 combination of such mental endowments of the ancestors in one 

 child. Of course something more is necessary, namely, the strength- 

 ening of certain of these hereditary endowments, but of this we shall 

 speak later. 



It is, however, not only the immediate ancestors, that is to 

 say, the parents, that have to be taken account of in this mingling 

 of hereditary contributions, but also those more remote. Not a few 

 characters in the child do not occur in either parent, but were present 

 in the grandparents, and their reappearance is called ' atavism ' or 

 ' reversion,' Let us consider this phenomenon in more detail, and 

 try to find out whether and how far it can be interpreted by 

 means of our theory. 



The simplest and clearest cases are again found among plant- 

 hybrids. It may happen, for instance, that a hybrid between two 

 species, when dusted with its own pollen, gives rise to descendants, 

 some of which resemble only one of the ancestral forms : thus we 

 have reversion to one of the grandparents. The explanation of this 

 lies in the different modes in which the reducing divisions are 

 effected ; if they take place in such a manner that all the paternal 

 ids of the hybrid are separated from the maternal ids, then the 

 result is germ-cells which are like those of the grandj)arents, that 

 is, those of the parent species, and these, if they happen to combine 

 in amphimixis, must give rise to a pure seedling of one or other 

 of the two ancestral species. This case occurs less rarely than was 

 formerly supposed, and than it could do if absolutely free combination 

 of the idants took place at reduction. If combination were quite 

 unrestricted, all other possible combinations would be likely to occur 

 as frequently as these. But recent experiments have showoi that, 

 in many plant-hybrids, the germ-cells of the hybrids which are 



