MENDELISM AND SEX 135 



which carries femaleness, meets a pollen-cell carrying 

 maleness, it is clear that if femaleness is dominant, 

 the resulting offspring will be female. But whereas 

 the male is pure maleness, the female is a hybrid, 

 carrying both maleness and femaleness. 



Similarly, the offspring resulting from fertilising 

 the egg-cells of B. dioica carrying either maleness or 

 femaleness with the pollen-cells of B. alba carrying 

 femaleness alone, are expected to consist of hetero- 

 zygous (hybrid) females and homozygous (pure) 

 females in equal numbers. That is, so far as visible 

 characters are concerned — for we cannot distinguish 

 these two kinds of females by inspection — the offspring 

 are expected to consist entirely of females. And 

 experiment shows that such is the case. 



In the reciprocal cross of the egg- cells of B. alba 

 carrying either femaleness or maleness fertilised with 

 the pollen-cells of B. dioica carrying maleness alone, 

 it is expected that one half of the offspring will be 

 heterozygous females and one half homozygous males. 

 And again experiment confirms our expectations, 

 in so far that the offspring does consist of an 

 equal number of males and females.* 



The application of Mendelian methods and inter- 

 pretation to the consideration of the experimental 

 results does, therefore, give us an intelligible and 

 consistent statement of the ascertained facts. No 

 previous theory has ever accomplished that. And 

 we may, I think, feel assured that at last we are 

 on the right road towards the elucidation of this 

 difficult but interesting problem. 



*It would he interesting to know whether B. alba when self -fertilised produces 

 fondle plants as icell as hertnaphrodites, as it should do nccording to this scheme. 



