Sex Determination in Phylloxerans and Aphids 343 
removal of the ovaries at an early age causes the development of 
‘“‘male”’ characters (somatic). The result shows unmistakably that 
the female in these groups has the capacity to produce both second- 
ary sexual characters. [It is also sometimes claimed that castra- 
tion causes the male to develop the characters of the female, and in 
favor of this view the retention of the high voice by eunuchs and 
the absence of a beard have been supposed toindicate an approach 
tothe female. It is, however, evident that these are juvenile charac- 
ters, and that castration has only suppressed the complete develop- 
ment of the male. Other cases have been cited that seem to their 
authors to show an approach to the female type, but the evidence 
is not as convincing as that in the case of the female. In the 
insects there seems to be no correlation between the development of 
the secondary sexual characters and the sexual organs, so that we 
cannot test the nature of the individuals in this way. 
In the crabs the evidence is as follows: 
In the crustacea (Carcinus, Inachus, Stenorynchus) there are ° 
certain facts according to Geoffrey Smith connected with parasitic 
castration that have been interpreted to mean, that the male 
assumes the secondary characters of the female when the testes are 
destroyed. Instead of the narrow abdomen of the male, the 
infected males have a broad abdomen more like that of the female‘ 
and the copulatory abdominal appendages of the male are wanting. 
Instead the corresponding parts are biramous like those of the 
female. It may appear, therefore, that the male is heterozy- 
gous and produces the female character when the male organ is 
suppressed. But the facts might possibly be interpreted in 
another way. The broad abdomen of the castrated male might 
be considered to correspond to the juvenile state. The only 
external structure cited by Smith that might seem to indicate that 
the characters of the castrated males are female rather than 
juvenile ones is the presence of hairs on the abdominal appendages 
of Inachus, absent in the young crab, but present in the adult 
female. Such evidence would not in itself be conclusive, since the 
presence of hairs may be due to increase in size or to a later moult 
rather than to latent female characters. ‘The claws of the male 
of Inachus also differ from those of the female, but here again the 
