438 



GEPHYREA 



others and forms the ovum. The mature sexual cells leave the 

 body through the nephridia. 



Bonellia and Hamingia present very interesting cases of 

 sexual dimorphism. In both genera the female is an animal of 



FIG. 222. An adult male Bon- 

 ellia i-iridis Rol. The original 

 was 1 '5 mm. long. The two 

 hooks have fallen off and 

 the nervous system is not 

 shown. (After Selenka.) a, 

 Generative pore with sper- 

 matozoa coming out ; b, an- 

 terior blind end of intestine 

 attached to the parenchy- 

 matous tissue by muscular 

 strands ; c, green wandering 

 cells containing chlorophyll ; 

 d, parenchymatous connective- 

 tissue ; e, epidermis ; i, intes- 

 tine ; j, vas deferens ; I, in- 

 ternal opening of vas deferens ; 

 , the left nephridium ; n, 

 spermatozoa in the body- 

 cavity. 



considerable size with the normal structure of the Echiuroidea, but 

 the male (Fig. 222) is a microscopic Planarian-like animal, which 

 lives in the mouth and in the nephridia of the female. Both in 

 Bonellia l and in Hamingia the male is provided with a pair of 

 hook -like ventral bristles ; these are wanting in the female 

 Hamingia. The surface of the male is ciliated, and the skin 

 1 This may not be true of all species. 



