PEDICELLATA. 



CLASS I. 



ECHINODERMATA *. 



THE Echinodermata are the most complicated animals of this 

 division. Invested with a well organised skin, frequently supported 

 by a sort of skeleton, and armed with points, or moveable and arti- 

 culated 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, but keeps up a commu- 

 nication with various parts of the intestine, and with the organs of 

 respiration, which are generally 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. 



ORDER I. 



PEDICELLATA. 



THE Pedicellate are distinguished by organs of motion exclusively peculiar 

 to them. Their skin is pierced with a number 

 of little holes, arranged in very regular series, 

 through which pass cylindrical and membranous 

 tentacula, each one terminated by a little disk 

 which acts like a cupping-glass. That portion 

 of these tentacula which remains within the body 

 is vesicular; a humour is effused through their 

 entire cavity, and is either propelled at the will 

 of the animal into the exterior and cylindrical 

 portion, which it distends, or returns to the interior vesicle, when the former 

 sinks and becomes relaxed. It is by thus elongating and shortening their 

 hundreds of little feet or tentacula, and by fixing them by their cup-like 



* The Radiaircs Echinodennes of M. de Lamarck. 

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