Fio. 371.— Organisa- 

 tion of Holotliuria 

 tutjulosa. Tlip blood 

 vascular system is 

 markeil black. 1, Oral 

 tentacles ; 2', stone 

 canals ; 3, water vas- 

 cular ring; i, Polian 

 vesicle ; 5, gonads ; (j, 

 longitudinal muscles ; 

 7, anterior section of 

 intestine ; 8, ventral 

 intestinal vessel ; 9, 

 radial water vessel ; 10, 

 vascular anastomoses ; 

 11, dorsal intestinal 

 vessel ; 12, filaments 

 and strands (of the 

 nature of both muscle 

 and connective tissue) 

 which attach the cloaca 

 to the body wall ; 13, 

 cloaca ; 14, cloacal 

 aperture (anus) ; 15, 

 middle section of the 

 intestine ; 16, posterior 

 section of the same : 

 17, right branchial tree; 

 IS, rete mirabile ; 19, 

 radial canal of the 

 water vascular system ; 



20, left brancliial tree ; 



21, tentacle ampulhe 

 (after Milne Edwards 

 and Cams). 



