loo MENDELISM chap. 



gametes Fg and fG. For on our assumption F and 

 G cannot enter into the same gamete. The series 

 of gametes produced by the F^ moths, therefore, are 

 fG,fg by the male and Fg,fG by the female. The 

 resulting F^ generation consequently consists of 

 the four classes of zygotes Ffgg, FfGg, f/Gg, and 

 ffGG in equal numbers. In other words, the sexes 

 are produced in equal numbers, the proportion of 

 rvoxva'dS. grossulariata to lacticolor is 3:1, and all of 

 the lacticolor are females ; that is to say, the re- 

 sults worked out on our assumptions accord with 

 those actually produced by experiment. We may 

 now turn to the results which should be obtained 

 by crossing the Fj moths with the lacticolor variety. 

 And first we will take the cross lacticolor female X F^ 

 male. The gametes produced by the lacticolor 

 female we have already seen to be Fg and fg, while 

 those produced by the Fj male are fG and fg. The 

 bringing together of these two series of gametes must 

 result in equal numbers of the four kinds of zygotes 

 FfGg, Ffgg,ffGg, ^"^Affgg, ie. of female grossulariata 

 and lacticolor, and of male grossulariata and lacticolor 

 in equal numbers. Here, again, the calculated results 

 accord with those of experiment. Lastly, we may 

 examine what should happen when the Fj female is 

 crossed with the lacticolor male. The F^ female, 

 owing to the repulsion between F and G, produces 

 only the two kinds of ova Fg and fG, and produces 

 them in equal numbers. Since the lacticolor male 

 can contain neither F nor G, all of its spermatozoa 

 must be_;^. The results of such a cross, therefore, 

 should be to produce equal numbers of the two 

 kinds of zygote Ffgg and ffGg, i.e. of lacticolor 



