ANNELIDA 



303 



m.retr. 



Fig. 209. Bonellia viridis. A, Female. B, Male from nephridium of female. 

 After Spengler. C, Sipunculus. From Shipley and MacBride. a. frilled 

 membrane surrounding the mouth ; al. alimentary canal ; al. degenerate 

 alimentary canal of male; an. anus; an.v. anal vesicle; ht. brown tube 

 (nephridium); ch. position of chaetae; cil.gr. ciliated groove; an. coecum of 

 gut; d.v. dorsal blood vessel; e. cut ends of intestine; g. anal glands; m.retr. 

 retractor muscle of anterior end ; M. mouth; n.c. nerve cord; nephr. nephro- 

 stome; oe. oesophagus; o. ovary; op. o male reproductive aperture; pr. 

 greatly enlarged prostomium; sp. spermatozoa. 



