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Show ANIMALIA RADIATA· 328 t of the tissue of their developmen from Polypi in the greater . which we place at the h Hydrostattca, Organs. The Acalep a k wn will perhaps form a nd of this class, w h en better no ' f · 1 conJ· ecture the unctions see parate one ; as yet however we on y of their singular organs. the fourth class, are those The PoLYPI, which compose th surrounded with tenta- . ls whose mou · fi 1 little gelatinous anuna etimes simple and som~ttmes o - Cula leads to a stomach som f vessels To thts class be- . · the form 0 • • lowed by intesttnes tn d animals with a fixe<l and . erable com poun long those mnum . d ed as marine plants. solid stem which were const er usually placed at the end . d Sponges are d . The Thethytre an . h not yet been discovere m of this class, although Polypt ave them. h fifth and last class of the Zoophy~a, The INFUSORIA, or t e . tence we have only dis- . b · gs whose ex1s . are those mmute em . e and which swarm m f the mtcroscop , . covered by means o h have merely a gelatmous Most of t em · stagnant waters. . ou h we commence the series body destitute of vtscera, a~th g ssed of visible organs of d speCies posse . with more compoun h 1 0 may hereafter const1· locomotion and a stomach : t ese a s tute a separate class. 329 CLASS I. ECHINODERMATA(!). The Echinodermata are the most complicated animals of this division. Invested with a well organized skin, frequently supported by a sort of skeleton, and armed with points, or movable and articulated spines, they have an internal cavity in which distinct and floating viscera may be perceived. A sort of vascular system, which it is true does not extend throughout the body, keeps up a communication with various , parts of the intestine, and with the organs of respiration, which are genera11y very distinct. Threads are also seen in several, which may act as nerves, but which are never arranged with the regularity and fixed order of those in the animals of the two preceding divisions of the Invertebrata. We divide the Echinodermata into two orders : those furnished with feet or at least with vesicular organs, so called on account of their fulfilling similar functions ; and those in which they are wanting. {1) The Radaires Echinodermes of M. de Lamarck. VoL. IV.-2 R |
