1IOLOTHUBOIDEA. 299 



The Holothurians are partly nocturnal in their habits, and live at 

 the bottom of the sea, for the most part in shallow places near the 

 coast, where they crawl slowly upon the bottom. The Synaptidce, 

 which have no feet, burrow in the sand. They feed on the smaller 

 marine animals, which, in the Dendrochirota, are carried to the 

 mouth by means of the branched, tree-like tentacles. The Aspido- 

 chirota fill their intestine with sand, which they eject from the anus 

 by means of the current of water from the respiratory trees. It is 

 worthy of notice that they (especially the Aspidockirota) can eject 

 through the anal opening the intestine, which breaks off easily 

 behind the vascular ring, and are able to renew it. The Synapta, 

 when irritated, are able to break their body into several pieces by 

 violent muscular contractions. 



Order 1. PEDATA. 



Numerous ambulacral feet, ivhich are sometimes arranged regularly 

 in the meridians, and sometimes distributed over the whole surface. 



Fam. Aspidochirotse. With shield-shaped tentacles. Holotliuria L. With 

 scattered ambulacral feet, which are conical on the dorsal side, and are without 

 suckers. H. tubulosa Gmel.. Adriatic and Mediterranean ; //. edulis Less., 

 the edible Trepang of the East Indian seas. 



Fam. DendrocMrotae. With tree-like branched tentacles. Cucvmaria 

 Blainv. Ambulacral feet arranged in regular rows. C. frondosa Gr. Psolus 

 Okcn. Ambulacral feet confined to the foot-like ventral surface of the trivium. 

 Ps. phantapus. Gr. 



Order 2. APODA. 



No ambulacral feet ; as a rule without respiratory trees ; the tentacles 

 are usually branched or pinnate. 



Fam. Synaptidae. Hermaphrodite and without respiratory trees. In the 

 skin there are wheel-shaped calcareous bodies or projecting masses shaped like 

 anchors, and affixed to calcareous plates. Synapta dif/itata Mntg. with anchor- 

 shaped calcareous bodies. J. Miiller discovered in their bodies parasitic cylin- 

 drical animals with spermatozoa and ova, which latter develop into small 

 shell-bearing Gastropods (Entoconclia mirabilig). Cliirodota Esch. Skin beset 

 with rows of small tubercles bearing calcareous wheel-shaped bodies. The 

 genus Molpadia Cuv. is furnished with respiratory trees. 



ENTEROPNEUSTA. 



The remarkable genus Balanoglossus must be placed here. It is 

 the representative of a class, Enteropneusta Gegenb.,* allied to the 

 Echinodermata, but usually classed with the Vermes, and presenting 



* A. Kowalevski. " Anatomic des Balanoglossus Delle Chiaje," Memoires da 

 VAcad. imper. des Sciences de St. Petersburg, Tom X., No. 3, 1866. L. Agassiz, 



