HEREDITY 



nance behave in different ways under different 

 circumstances, at one time dominating com- 

 pletely, at another only feebly, and at other 

 times not at all. 



Undoubtedly the chief condition affecting 

 dominance is the nature of the gamete with 

 which a union is made in fertilization. In 1905 

 (Carnegie Inst. PubL No. 23) I described a 

 case in which a particular guinea-pig (male 

 2002, shown in Fig. 32) having a rough or 

 resetted coat gave a varying result in crosses. 

 In crosses with most smooth animals his rough 

 character dominated completely (see Fig. 24, 

 which shows a son of the male 2002 by a smooth 

 mother), but with one particular smooth ani- 

 mal the dominance was very imperfect in all 

 the young (Fig. 36), while with a second it 

 was imperfect in half the young. The conclu- 

 sion was drawn that gametes vary in potency, 

 and that parents, too, differ as regards the 

 potency of the gametes which they produce, 

 some individuals producing gametes all of which 

 are relatively potent, others producing gametes 

 only half of which are potent, while still others 

 produce gametes none of which are potent. 



98 



