RW. 



.B.K. 



FIG. 40. Anatomy of Holotlntria tubiilosa after M. Edwards, somewhat 

 modified. M, tentacles; F, ampullae of the tentacles; RW, radial ambulacral 

 canal; W, rete mirabile; L. K, left water lung; R. K, right water lung; G. A, 

 anastomosis of the blood vessels; HD, posterior section of intestine; MD, mid- 

 dle section of intestine; S, hydrophone canal; Wf, ring canal; PB, polian 

 vesicle; G, gonad; LM, longitudinal muscles; VD, ventral blood vessel; 

 DD, dorsal blood vessel; BK, dilator of the cloaca; A', cloaca; A, anus. 



