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 papille, 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 thé 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 cu/-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. Pouchet 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 
