5TAk-KISUES. 



43 



term, as applied to all those creatures whose integument is 

 coriaceous or prickly. 



The Echinodcrraata exhibit, in many respects, an entire 

 contrast to the Acalopliaj. That of their covering is obvious 

 to the most cursory observer; that of their internal structure 

 Is not less remarkable. The anatomist is baffled by the 

 seemuig simplicity and uniformity of texture in the gektiuoua 



Fig- •28.— STAR-Pisn. 



Radiaries; in the harder, or spine-clad species, the extreme 

 complexity and diversity of their constituent parts is found to 

 bo no less pe'-plexing.* 



All the animals of this class are marine, and in their adult 

 state move freely about. The sexes are distinct, and the 

 young are produced from ova, which, in a certain stage of 

 their development, become covered with minute cilia. They 

 then come forth as ciliated gemmules, are diffused over the 

 bottom of the sea, and undergo a series of transfonnations 

 analagous to those described in the Medusa;. The obsen-ations 

 of a Norwegian naturalist f have made us aware of an interest- 



" Owen, page 112. 



t Sars, vide Aiinals Nat Hist. Oct. 1814, page 233, and plate III. 



