EFFECTS OF AMPHIMIXIS ON ONTOGENY 279 



minants of other colours ; two-thirds of the ids of the mother 

 on the other hand consist of bhie, and one-third of brown deter- 

 minants. The iris of the child will therefore most probably 

 be brown, for in its formation nine-tenths of the determinants 

 of the father will co-operate with one-third of the determinants 

 of the mother, which are homodynamous with these. The pre- 

 dominance of the brown determinants would also, however, still 

 be assured if the maternal ids contain no determinants at all of 

 this colour, but only red or green ones, — supposing that red or 

 green pigment cells occurred in the human iris. For in this case 

 nine-tenths of the paternal determinants would be opposed to 

 various small groups of heterodynamous determinants of the 

 mother. The latter might possibly modify the brown colour 

 which would be produced by groups of paternal determinants 

 alone, for they also control part of the cell-body ; but it is quite 

 as conceivable that they might be completely overcome by the 

 paternal determinants, and thus excluded from the control of 

 the cell. We cannot, as already stated, at present judge as to 

 the result of the struggle of the parts in individual cases, but 

 there is no doubt that, provided the controlling power of the 

 determinants is similar, the number of the latter is of the first 

 importance. 



Since, therefore, the nature of the combination in the germ- 

 plasm is different in every individual in consequence of sexual 

 reproduction, the number of homodynamous determinants of 

 any particular characteristic must also be different in every case. 

 It will be, shown in the chapter on variation that processes of 

 selection may even bring about an increase or decrease in the 

 number of the homodynamous ids of individual characters, 

 although these are never of sufficient biological importance to 

 give rise to specific characters. 



The same competition of forces must take place in the case of 

 individual as in that of specific characters. A child may inherit 

 the colour of the eyes from its father, and the shape of the 

 mouth from its mother, just as in a plant-hybrid the form of the 

 leaf may resemble that in the paternal, and the flower that in 

 the maternal plant. In both instances the character is inherited 

 from that parent in which the group of idants contains a pre- 

 ponderating majority of homodynamous determinants of this 

 character. When this is the case, this majority preponderates 

 over the scattered minority derived from the other parent. 



