RADIARIES. 201 



cast upon the shore they dissolve into a fluid 

 exactly resembling sea water. 



The Echinoderms 1 form the second order of 

 the Radiaries. This name was first given by 

 Bruguieres to a class formed solely of Linne's 

 genera Echinus and Asterias, but Lamarck has 

 added others to it. He has divided it into three 

 sections, the Stelleridans, Echinidans, and Fis- 

 tulidans ; in all these the outward envelope is of 

 a much harder substance than in the gelatines, 

 in the first and last of these sections resembling 

 leather, and in the other, consisting of the sea- 

 urchins, 2 it is a crust in some degree like that of 

 crabs and lobsters. The animals of this Order, 

 though their nervous system is obscure, have a 

 high degree of muscular motion and are fitted 

 with motive organs. 



To look at a star-fish one would wonder, at 

 first, how it could move progressively, its rays 

 seeming not at all calculated for that purpose, 

 this however is wisely provided for. Those of 

 one family send forth a number of tentacles, 

 from a furrow in the underside of the rays into 

 which their body is divided, each terminating 

 in a cup-shaped sucker, which they can lengthen 

 or shorten, and fix to hard bodies. These ten- 

 tacles, or legs, as Cuvier calls them, are similar 



1 Echinodermata. z Echinus. 



