ECHINODERMATA. 
257 
Class III, —Ctenophora. 
The Ctenophora (as the Pleuro- 
brachia , Cesium , and Beroe) secrete 
no hard deposit. They are trans¬ 
parent and gelatinous, swimming on 
the ocean by means of eight comb¬ 
like, ciliated bands, which work like 
paddles. The body is not contrac¬ 
tile, as in the Jelly-fishes. They are 
considered the highest of Coelente- 
rates, having a complex nutritive ap~ fig. 209 .-Actenophore (rieu- 
paratus and a definite nervous sys- size, 
tern. 
Subkingdom IV. —-Echinodermata. 
The Echinoderms, as Star-fishes and Sea-urchins, are dis¬ 
tinguished by the possession of a distinct nervous system (a 
ring around the mouth with radiating branches); an all- 
Fig. 2U).— Forms of Echinoderms, from radiate to anmilose type: a, Crinoids; b, 
Ophiurans; c, Star-fish; d, Echini; e, Holothuriaus. 
mentary canal, completely shut off from the body-cavity, 
and having both oral and anal apertures; a water-vascular 
17 
