433 



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 viridis Rol. The ori- 

 ginal was 1*5 mm. long. 

 The nervous system is not 

 shown. (Alter Selenka.) a, 

 Generative pore with sper- 

 matozoa coming out ; b, an- 

 terior blind end of intestine 

 attached to the parenchy- 

 matous tissue by muscula 

 strands ; c, green wanderir 

 cells containing chlorophyll 

 d, parenchymatous connective 

 tissue ; e, epidermis ; i, intes 

 tine ; j, vas deferens ; I, in- 

 ternal opening of vas deferens : 

 m, the left anal vesicle 

 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 1 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 is not true of all species. 



