114 



SEX INHERITANCE 



assume that several genes are present that produce hke 

 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, 



Fig. 3t)E. — 1, 2, adult normal male; 3, 4, adult normal female; 5, G, 

 infected male that has assumed female characters. (After Geoffrey Smith.) 



that when males (Fig. 36 E, 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). 



