No. 512] 



NOTES AND LITERATURE 



503 



carried by the germ we introduce a conception entirely foreign 

 to the whole Mendelian scheme. Then 1 is no evidence of selec- 

 tive fertilization in this sense known elsewhere and it seems a 

 very questionable advantage to introduce the factor inlo the 

 Mendelian process. The evidence that Cuenot brought forward 

 in a second paper to show that selective fertilization takes place 

 is open to criticism. He points out that since half the eggs 

 can not be fertilized by half the sperm, there should be fewer 

 young born when yellow is crossed with yellow than when yellow 

 is crossed with any other color. His data show in fact a lower 

 birth rate for yellow by yellow than when yellow is fertilized 

 by other colors. Two objections to this argument may be ad- 

 vanced. First we must suppose that there are sufficient sperm 

 present to fertilize the few eggs set free at each menstruation. 

 Even if a yellow egg is not fertilized by a yellow sperm it should 

 be fertilized by one of the other sperms. Second the fertility 

 of the yellow mice is in my experience lower than that of other 



In order to avoid the hypothesis of selective fertilization and 

 accepting Cuenot's statement that pure (homozygous) yellow 

 mice do not exist, I suggested tentatively that the yellow-pro- 

 ducing factor is not allelomorphic to the other colors, but that 

 the germ cells of yellow mice are represented by the symbols 

 Y(B), B(Y), to take a single example; in other words that 

 yellow and the other color, black in this case, alternately domi- 

 nate and recede. In this way the numerical results follow. I 



similar mechanism might explain the alternate nature of the 

 germ cells in all Mendelian cases and pointed out how this 

 view could be tested. I have made one such test with entirely 



abandoned. 



An experiment that I made with yellow mice showed, how- 

 ever, that the yellow bearing germ cells of yellow mice do carry 

 other color factors than yellow, and this result, which is not 

 in harmony with Cuenot's assumption for the behavior of yellow 

 color in the gametes, offers the possibility of a di *^ rent ex P lana " 



known ancestry— it carried black only. Some of the offspring 

 were yellow. Two of these inbred gave yellows, blacks, choco- 

 lates and albinos. Obviously the yellow bearing germ cells 



