rt or rectum, is a 



PHYLUM ANNULATA 



453 



narrow groove. Twisted round the posterior 

 part is a long narrow ccecum, which 

 opens into the beginning of the 

 rectum. Two groups of rectal 

 glands occur close to the anal 

 opening. 



The nervous system (Fig. 355) 

 differs considerably from that of 

 the rest of the Annulata. There 

 is a relatively small bilobed cere- 

 bral ganglion situated on the dorsal 

 aspect just behind the tentacular 

 circlet, to which it gives off on 

 each side several pairs of nerves. 

 -recb 



oes 



FIG. 354. Dissection of the internal organs 

 of Sipunculus nudus. dors, ret,: 

 dorsal retractor muscles of the intro- 

 vert ; int. intestine ; m. n. co. muscles 

 accompanying the nerve cord ; n. co. 

 nerve cord ; neph. nephridium ; <*. 

 oesophagus ; rect. rectum ; tent, tenta- 

 cular fold. (After Vogt and Jung.) 



FIG. 355. Anterior part of the nervous system 

 of Sipunculus nudus. can. o. ccb, cere- 

 bral organ ; corns, ce, ossophagal connective ; 

 n.m i'. ret, nerves to retractor muscles ; n. spl. 

 splanchnic nerves ; n. ta, 1-lt, nerves to ten- 

 tacular fold ; /, //, nerves from ventral cord. 

 (After Ward.) 



