330 



ORGANS OF DIGESTION. 



cavity, and connected to the sides of the abdomen by a vas- 

 cular mesentery, passing from the one aperture to the other, 

 as seen in the annexed figure of the holothuria elegans 

 (Fig. 114.) by W. Bell. The mouth (114. a.) is generally 

 surrounded with long tentacula in form of ramose tufts (holo- 

 thuria of Lam.) in others the tentacula are simple, and 

 expand only at their free ends (fistularia of Lam.), and some- 

 times long saliyary follicles (b.) open into its parietes. The ten- 

 tacula, capable of complete retraction within the oral aper- 

 ture, are supported by the circle of osseous plates to which 

 the strong longitudinal muscular bands of the trunk are 



FIG. 114. 



