HOLOTHUROIDEA. 



347 



<Fio. 336. Anatomy of Caudina arenata. (After Kingsley.) a, anastomoses of dorsal 

 blood-vessel; b, branchial tree; d, dorsal blood-vessel; /, mesenterial filaments; 

 g, genital opening; ?, alimentary canal; I, longitudinal muscles; m, mouth: <>, 

 genital duct; p, pharyngeal ring ; ?, gonads, cut away on right side; f, ampullae 

 of tentacles ; v, ventral blood-vessel. 



