114 SEX INHERITANCE 
assume that several genes are present that produce like 
effects in the male but different effects in the female, 
that is, the characters are sex-limited in development. 
PARASITIC CASTRATION AND SECONDARY 
SEXUAL CHARACTERS 
It was first shown by Giard (1886) and later 
confirmed by Geoffrey Smith (1906) and others, 
2 
Fig. 36E.—1, 2, adult normal male; 3, 4, adult normal female; 5, 6, 
infected male that has assumed female characters. (After Geoffrey Smith.) 
that when males (Fig. 36 EH, 1-2) of certain crabs 
are parasitised by other crustaceans, such as Pelto- 
gaster, Sacculina, etc., they develop the secondary 
sexual characters of the female (Fig. 36 E, 5-6). 
