486 



ZOOLOGY 



SECT. 



which is separated by spaces into a series of parallel bands. 



Between the bundles of the longitudinal 

 f en l layer of muscle runs a system of canals 



which communicate with the body- 

 cavity by transverse branches. 



There is a spacious ccelome, but it 

 is traversed in all directions by fila- 

 ments and strands of connective-tissue, 

 with which are mixed very fine muscular 

 fibres ; these mostly run from the wall 

 of the body to the alimentary canal. 

 Floating in the coelomic fluid are (1) 

 colourless amoeboid corpuscles ; (2) 

 rounded biconcave corpuscles, faintly 

 dors. retr-1iM^i'lfiM]L-rcc coloured by a substance, hccmerythrin, 



m.n.co 



dorsretr- 



ocs 



n. 



ret 



FIG. 403. Dissection of the internal or- 

 gans of Sipunculus nudus. dors. retr. 

 dorsal retractor muscles of the intro- 

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

 accompanying the nerve-cord ; n. ro. 

 nerve-cord : neph. nephridium ; ces. 

 oesophagus ; rect. rectum ; tent, tenta- 

 cular fold. (After Vogt and Jung.) 



FIG. 404. Anterior part of the nervous system 

 of Sipunculus nudus. can. o. ceb. cere- 

 bral organ ; corns, a?, oesophageal connective; 

 n. mu. ret. nerves to retractor muscles ; n. xpl, 

 splanchnic nerves ; n. ta. 1-4, nerves to ten- 

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

 24, main mass of brain. (After Ward.) 



