IX 



PHYLUM ECHINODERMATA 



37J 



and sends off five radial vessels, as well as dorsal and ventral vessels 

 (int. ves.) accompanying the enteric canal, and a plexus surrounding 

 the left respiratory tree. 



ci.rc-fUL8 

 cu,v ory 



FIG. 300. Internal organs of a Holothurian as seen when the body -wall is divided along^the 

 middle of the dorsal surface : 6. ;c. body-wall ; circ. ntcs. circular layer of muscle ; cl. cloaca : 

 rl. <>j:>. cloacal opening with five teeth ; Tcr. orii. Ciivieran organs; gen. np. genital aperture ; 

 iifii.iiii. genital duct ; </.:/i. ;//. genital gland ; iiit. intestine; tntfr. oss. inter-ambulacra! ossi- 

 cles : i, it. ves. intestinal vessels ; l<>n;i. mus. longitudinal band of muscle ; mail. cnii,. madreporic 

 canals ; tries, niesentry ; pol. res. Polian vesicles ; rail. //>. radial ambulacral vessel ; ri. U. 

 ves. ring blood-vessel ; i-)i. respiratory trees ; ring-ves. riiig-vessel of the ambulacral system ; 

 stom. stomach. (After Leuckart.) 



The coelome contains a fluid in which float numerous amcebo- 

 cytes similar to those of the Starfish, and also a number of 

 flattened nucleated corpuscles containing a red colouring matter 



B B 2 



