THE DETERMINATION OF SEX 213 



According to Smith, parasitic castration is performed 

 on the crab Inachus, which is found in the Bay of 

 Naples, by a cirripede, Sacculina. The male crab 

 of this species has one large claw and a narrow abdo- 

 men, while the female has no large claw, but a broad 

 abdomen. When Sacculina parasitizes the female, the 

 secondary sexual characters of the female are stunted, 

 but not materially changed. When, on the contrary, 

 the male is parasitized, it not only loses its distinctive 

 large claw in subsequent molts, but it also takes 

 on the broad abdomen of the female (Fig. 64). This 

 apparent anomaly is quite explainable upon the as- 

 sumption that the female is homozygous for sex 

 and the accompanying secondary sexual characters, 

 while the male is heterozygous. When maleness is 

 destroyed in the male by the castrating parasite, 

 therefore, the femaleness that is latent in this sex 

 becomes manifest through the appearance of female 

 secondary sexual characters ; but when the female is 

 castrated, no other secondary sexual characters than 

 those already present make their appearance, since 

 only femaleness is present in the homozygous female 

 sex. 



c. Sex-limited Inheritance 



Additional evidence that sex is a character depend- 

 ing upon determiners which behave in Mendelian 

 fashion is furnished by what is called sex-limited 

 inheritance. There are certain characters known as 

 sex-limited characters that are in no sense to be con- 

 fused with secondary sexual characters which appear 

 to be always linked with the determiner for either one 



