258 THE OCEAN WORLD. 



star-fishes walking upon the sand. A day rarely passes without 

 one of them being thrown upon the strand by the tide, and then 

 abandoned by the retreating waters. Generally they are left dead : 

 this is not always the case, however; they are sometimes only 

 benumbed. Place them in a vase full of sea-water, or simply in a 

 pool on the shore, and you will sometimes see them recover from 

 this death-like condition, and execute the curious movements of 

 progression which we have described. The motions of an Asterias 

 thus saved form a very curious spectacle. 



The mouth of this animal is situated on the lower surface of the 

 disc. At this point the constitutive pieces of the body skeleton leave 

 a circular space, covered by a fibrous resistant membrane, pierced at 

 the centre by a rounded opening. This opening is sometimes armed 

 with hard papillae, which play the part of teeth. The mouth almost 

 directly abuts on the stomach, which is merely a globular sac, filling 

 nearly all the central portion of the visceral cavity. 



" Thus," says M. Milne-Edwards, " in Asteracanthion glacialis the 

 stomach is globular, but imperfectly divided into two parts by a fold 

 of its internal membrane ; the first chamber, thus limited, appears to 

 be more especially devoted to the transformation of the elementary 

 matter into a liquid paste, which passes, in small portions, into the 

 upper chamber. This is passed onward through a small intestine, 

 and communicates laterally with five cylindrical prolongations, which 

 each divide themselves again into two much elongated tubes, furnished 

 with a double series of hollow branches each terminating in a cul-de- 

 sac" These organs are protruded into the interior of the rays or 

 arms of the Asterias. 



Imagine, then, an animal bearing digestive tubes in its arms the 

 same portion serving to lodge both the organs of digestion and pro- 

 gression. What lessons in economy does not the study of Nature 

 teach us ! The products of digestion find an absorbent surface of 

 great extent in the rays of the Asterias. They ought necessarily to 

 pass rapidly from it into the circumjacent nourishing fluid. 



The star-fishes are very voracious ; they even attack molluscs 

 which are covered with shells. M. Pouch et mentions having taken 

 eighteen specimens of a species of Venus intact, each being six lines 

 in length, from the stomach of one large Asterias which he dissected 

 upon the shores of the Mediterranean. 



It is now even said that the star-fishes eat many oysters. Ancient 

 naturalists were not ignorant of this fact \ but they believed that the 

 star-fish waited for the moment when the bivalve would open its valves 

 to introduce one of its rays into the opening. They imagined that 



