276 RECENT CYTOLOGY 
tion. Amongst these are the observations made by 
Doncaster on certain moths, which gave curiously 
complex results explicable on the above supposition 
as to the nature of sex. 
In the human race colour-blindness is common in 
men, but rare in women. Men with normal sight 
cannot transmit colour - blindness, but women with 
normal sight can. According to Bateson, only seven 
cases are known of colour-blind women, and these had 
in all seventeen sons, all of whom were colour-blind. 
Colour-blindness must therefore be supposed to be due 
to the presence of a dominant allelomorph, and its 
non-appearance in women must be caused by the 
presence of another dominant factor which is epistatic 
to the factor for colour-blindness. It has been sug- 
gested that the counteracting element is none other 
than the factor for femaleness itself. 
Old and impotent females among the higher animals 
are known sometimes to assume some of the secondary 
characters of the male sex. This power suggests the 
presence of the male element as a previously latent 
factor in their constitution. On the other hand, the 
supposed female characters assumed by castrated 
males can probably be accounted for as the result 
of arrested development, without any necessity for 
assuming the presence of a female factor. 
It is not necessarily to be supposed that the above 
description of the facts of sex-determination will hold 
good for every kind of organism. In fact, Correns 
has produced evidence which seems to show that in 
