Echinodermata. 335 



lining membrane of the ray, and are called mesenteries. 

 From the pyloric stomach a slender intestine extends up 

 to the aboral wall, a little to one side of the center. Its 

 opening is hard to find and in some starfishes is entirely 

 obliterated. There are no jaws nor any teeth in the 

 starfish. 



The Starfish's Food and Mode of Eating. Starfishes feed 

 chiefly on mollusks, especially on oysters and mussels. 

 The starfish arches the body over the oyster, and then 

 turns its stomach inside out and around the soft body of 

 the oyster, and, after digesting it, withdraws the stomach 

 again. This seems an odd way of eating, but certainly it 

 is an economical way, for the starfish takes only what it 

 can digest and absorb. 



Damage done to Oysters. The starfish is a very vora- 

 cious animal, and the injury done by it to the oyster indus- 

 try is very great. The oystermen have learned that they 

 must make effort to keep the oyster beds clear of starfishes. 



How Starfishes recover after Mutilation. A starfish 

 torn in two will grow, and may make two complete star- 

 fishes. The oystermen know that it will make a bad 

 matter worse to tear the plunderer into pieces and throw 

 them back into the water. Experiments show very great 

 power of recovery after mutilation. Frequently one finds 

 starfishes with one ray missing, or even two or three. 

 Occasionally the collector finds a specimen with but one 

 fully developed ray, the other four having been lost. Four 

 new rays may, perhaps, be started, which in course of time 

 will grow to full size. 



The Body Cavity. The starfish is a decided advance 

 on the coelenterate type of structure in having a distinct 

 body cavity, separate from the digestive tube. 



