158 HEREDITY AND SEX 



The infected males ''show every degree of modi- 

 fication towards the female type." The legs are small, 

 the abdomen broad, the stylets reduced, and the 

 typical biramous appendages with hairs appear. 



When the female crab is infected she does not change 

 'Howard" the male type, although the ovary may 

 be destroyed. The only external change is that the 

 abdominal appendage may be reduced. 



In a hermit crab, Eupagurus rneticulosus, infected by 

 Peltogaster curvatus, similar results have been obtained. 

 The infected male assumed the ordinary sexual char- 

 acters of the female, but the females showed no change 

 towards the male. 



In these cases it seems probable that the testes of 

 the male suppress the development of the secondary 

 sexual characters that appear ordinarily only in the 

 females. The case is the reverse of that of the birds 

 and different again from that of the mammals. 



In birds and mammals the secondary sexual charac- 

 ters are in many cases directly dependent on the in- 

 ternal secretions of the sex glands. These secretions are 

 carried alike to all parts of the body, hence the absence 

 of bilateral gynandromorphs in these groups. 



adult male; 3, male infected with sacculina, showing reduction of chela 

 and slight broadening of abdomen; 4, 5, showing attenuated copulatory styles 

 and slight hollowing out of abdomen; 6, under side of abdomen of a similar 

 male specimen, showing reduction of copulatory styles and presence of 

 asymmetrically placed swimmerets characteristic of female; 7, infected 

 male which has assumed complete female appearance; 8, under side of 

 abdomen of 7, showing reduced copulatory styles and swimmerets; 9, under 

 side of abdomen of similar male specimen with well-developed copulatory 

 styles and swimmerets; 10, adult female, normal; 11, under side of abdomen 

 of 10, showing swimmerets and trough-shaped abdomen; 12, under side of 

 abdomen of infected female, showing reduction of swimmerets; 13, immature 

 female showing small flat abdomen; 14, under side of abdomen of 13, 

 showing flat surface and rod-like swimmerets. (After Geoffrey Smith.) 



