ECHINODERMA TA 251 



and the tube-feet. In Synapta ten auditory vesicles contain- 

 ing numerous otoliths have been described at the base of the 

 radial nerves. 



The generative organs are either a single gland situated at 

 the left of the dorsal mesentery, or a double gland, one on each 

 side of it ; the glands are continuous with a single duct, which 

 opens in the dorsal middle line close to the base of the ten- 

 tacles. With one or two exceptions, the Holothuroidea are 

 dioecious. 



The young of one species, Gucumaria erocea, found near 

 the Falkland Isles, are attached in rows on each side of the 

 dorsal ambulacrum. The early stages of developement ap- 

 parently take place rapidly, and the embryos are arranged in 

 position by the tube-feet of the ambulacrum. 



In the East Indies some species form an article of com- 

 merce under the name of BSche-de-mer. They are dried and 

 sold to the Chinese, who use them in the preparation of soup. 



The Holothuroidea are classified as follows : 



I. AcTiNOPODA. — Badial canals present in the water-vascular 

 system. 



a. Aspidochirotae. — The tentacles are peltate in form, 

 respirator]/ trees are present. Holothuria, Miilleria. 



h. Elasipoda. — Tentacles as above. The dorsal tube -feet 

 produced often info very long stiff processes. Bespira- 

 tory trees rudimentary or absent. Stone canal sometimes 

 opens to the exterior. Deima, Elpidia. 



c. Dendrochirotae. — The tentacles have a dendriform shape. 



Gucumaria, Thyone. 



d. Molpadiidae. — The tentacles are simple or pinnate. The 



radial canals bear tenta/iles, but no other tube -feet. 

 Molpadia, Caudina. 



II. Paeactinopoda. — The tentacles are pinnate. No radial 

 canals, no tube-feet, no respiraiovy trees. Synapta, Chirodota. 



