139.- 



-Dissection of Holothurian (Hohthuria tubulosa) from 

 the ventral surface. 



/., Tentacles surrounding the mouth ; /., scattered tube-feet of 

 ventral surface ; c., calcareous ring surrounding the food canal ; 

 #., ampullae of tentacles (modified tube-feet); r., circular vessel 

 surrounding the gullet, giving off the branched stone canal (stj, 

 the single Polian vesicle j^), and the Jive radial canals (r.c.), 

 which run forwards, pass through the calcareous ring, and then 

 curve outwards to run on the surface of the longitudinal 

 muscles (l.m.) along the radial areas. Of the five longitudinal 

 muscles, one only is marked. *., The gut cut through at the 

 beginning of the first loop; #*., the mesentery which attaches 

 the gut to the body wall, showing the course of the gut ; g., 

 the other end of the gut ; cl., the cloaca bound down by muscles ; 

 ., the anus ; r.t., the jight respiratory tree the left is cut short 

 close to its origin ; ov., the ovary. The blood vessels are not 

 shown. 



