W. Bateson and R. C. Punnktt 



189 



that of the white eye recorded by Morgan in Drosophila^ clearly point 

 to the existence in those cases of a repulsion between a factor for 

 maleness (M), and factors respectively for colour-blindness and for the 

 red eye. The operation of the system of sex-limitation is similar in all 

 these examples, the only difference being that in the one group the 

 repulsion is from the factor F, in the other from the factor M. 



iiPPf 



gives 

 gametes 



iPf] 



[9] 



lippFf 



gives 

 gametes 



\ipF 



[9]Iippff 



gives 

 gametes 



^Pl\ 



ipF] 



I I 



U^iiPpS iiPpFfii^ 



gives 

 gametes 



[ IPf\ 

 \ipf J 



gives 

 gametes 



lippffU\ 



gives 

 gametes 



Ipf 



iPF% 



Ipf 



ipf S 



Ipf 

 ipF^ 



Ipf 

 ipf 6 



Fig. 3- 



Recognition of the existence of factors both for femaleness and for 

 maleness of course involves the assumption that ova bearing F can only 

 be effectively fertilised by sperms not bearing M, and vice versa. For 

 that supposition no independent evidence yet exists, and we note that 



1 Morgan, Science, 1910, N. S. xxxii. p. 120. 



