F. HOLOTHUROIDEA. 



349 



The regenerative powers of these animals are of interest. In unfavor- 

 able conditions (hence in preserving the animals in alcohol without nar- 

 cotization with chloral) they void the whole viscera and yet may live and 

 reproduce the lost parts. In certain species are found a few parasites. 

 One or two harbor a small fish (Fierasfer) in their cloaca and branchial 

 trees. A parasitic snail, Entoconcha mirabilis, lives in one species of 

 Synapta, and a mussel, Entovalva mirabilis, in another. 



Order I. Actinopoda. 



Radial canals present, sending branches to the tentacles and am- 

 bulacra when present. Divided into Pedata, with ambulacra, and Apoda. 

 without. The PEDATA include the HolothuridsB with peltate tentacles. 



FIG. 338. Cucumaria frondosa, sea cucumber. (From Emerton.) 

 Holothuria * in warmer waters, one species furnishing the trepang of 

 Chinese markets. The CUCUMARIID^E represented in our waters by Cucu- 

 maria * (Pentacta) with regular rows of ambulacra, Thyone * with them 

 scattered, and Psolus* scaly with a creeping disc. The deep-sea ELA- 

 SIPODA belong to the Pedata. The APODA are represented by Gaudina * 

 (fig. 336) and Molpadia* 



Order II. Paractinopoda. 



No radial canals nor ambulacra. Tentacular canals arising from ring 

 canal. Myriotrochus* Synapla* Oligotrochus* (fig. 339). 



