CHAP. IV. MOTIONS OP RADIATED ANIMALS. 125 



(149-) Of the radiated animals, little can be said: 

 the motions of the Echinidce, or sea eggs, are effected 

 by means of the movable spines with which their shells 

 are furnished, and which, although short in that part 

 which reposes upon the ground, are yet so numerous as 

 to effect this object : these animals, however, move but 

 very little, as they prefer remaining in the little clefts 

 and hollows at the bottom of the sea. The Asterida, 

 or star-fish (fig. 43.), are much more active animals ; 



the numerous soft suckers by which the mouth and the 

 centre of these rays are furnished, seem to enable them 

 to change their habitation more frequently. There is 

 reason, also, for believing that several of those whose 

 rays or arms are very long and slender, can use these 

 members to swim with : they are, at all events, highly 

 flexible ; and star-fish of this form are not unfrequently 

 met with at such a distance from land, and where the 

 sea is so deep, that they must either have been drifted 

 with sea-weed, or have used their arms as swimmers. 

 It frequently happens, also, even on the British coasts, 

 that great numbers of star-fish are cast upon the shore 

 at a single ebb of the tide, as if a company of them had 

 been thus wrecked, while, at other times, not one is to 

 be seen for weeks. On returning again to the Acrita, 

 or polypes, by means of the intestinal worms, we see 



