V. HOLOTIIUROIDEA. 



3 19 



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. 

 Oae or two harbor a small fish {Fierasfer) in their cloaca and branchial 

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

 Sijnapta, and a mussel, Entovalva mirabUis, 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 Holothuridfe with peltate tentacles. 



^3 X 



Fio. 338.— Ci(cni7iai-ia frondosa, sea cucumber. (From Emerton.) 

 Eolotlturia* in warmer waters, one species furni.shing the trepang of 

 Chinese markets. The Cucdmariid/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. Mijriotrochus* Syrmpta* Oligoti-odais* (iig. 339). 



