582 
GEOFFREY SMITH. 
while females are incapable of assuming male characters. It 
is doubtful, however, whether this particular ‘ Meudelian ’ 
interpretation can be applied generally, because in some 
animals, e. g. the bee, it appears that the egg by itself is male 
and only becomes female through fertilisation, while in many 
Cladoceraand Aphidesfemales gave rise parthenogenetically to 
males. It appears, therefore, that the primary mechanism of 
sex determination may be vai'iouslj’’ distributed in the germ- 
cells” ([5] ‘‘ Rhizocephala,” ‘Fauna and Flora des Golfes von 
Neapel,’ Monogr. 29, p. 89, 1906). 
In the above words I believe that the following Mendeliau 
theory of sex is clearly stated : 
(1) That in certain species of animals (e. g. Inachus and 
other Crustacea) the male is a heterozygote of the composition 
(J ? , while the female is a pure recessive of the composition 
? ? . 
(2) That the sexual constitution is not necessai-ily the same 
in all species of animals, e. g. in the case of the Cladocera, 
where the female is proved to be a heterozygote owing to her 
capacity for producing both males and females partheno- 
genetically. 
In excuse for recapitulating these statements it may be 
pleaded that, owing to their appearance in a publication 
principally devoted to morphological studies, they have not 
been referred to by subsequent writers who have indepen- 
dently arrived at the same Meudelian theory of sex. 
Thus, Professor Bateson and Mr. Punnett (1908), in offer- 
ing an interpretation of the striking results obtained by 
Doncaster in his breeding experiments with the currant moth, 
have suggested that in this case the female is a heterozygote 
(c^ $) and the male a homozygote (c^ (?). The reason for 
this interpretation is as follows : The common currant moth. 
Abraxas gross u la riata, occasionally gives rise to a pale- 
coloured vai’iety, lacticolor, and this variety has been 
hitherto supposed to be confined to the female sex. Doncaster 
made, among others, the following crosses : 
(1) Lacticolor ? x grossulariata gave cl and ? 
