30 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



oysters which it devours. The extent of this loss is difficult 

 to estimate, and the reader is referred to page 33 for an account 

 of the injuries thus caused. 



The most usual food for all the species consists of moUusks 

 and crustaceans, of which the various species of mussels, the 

 oyster, the two common species of clams, and barnacles, furnish 

 the principal supply. Univalves, or sea snails, of various species, 

 and other invertebrates, are devoured whenever they can be 

 secured; and indeed almost any small animal when injured or 

 dead may be eaten. The larger starfishes may even devour small 

 individuals of the same or of different species. The common 

 starfish is occasionally of actual benefit in that it devours the 

 univalve known as the oyster drill (UroscUpinx cinerea), which 

 is itself a serious enemy of the oyster. But it does this only 

 when oysters or other bivalves are not obtainable. 



The starfish secures its prey by seizing it with the tube-feet 

 and then drawing it toward the mouth. The mouth, however, 

 is itself of small size as compared with the body of the star- 

 fish, being only about one-fourth to three-eighths of an inch in 

 diameter in a moderately large animal. Only objects of small 

 size can therefore be taken directly into the stomach. If the 

 prey be too large to pass the mouth, which is the case with 

 the greater part of the food, the soft, sac-like stomach is everted 

 from the mouth and wrapped around the prey, after which 

 digestive fluids are poured out and digestion ensues. After the 

 absorption of the nutritive substances contained in the body 

 of the prey, the stomach is again drawn into the body of the 

 starfish, by means of a special set of retractor muscles. 



If a large bivalve be secured, as a large oyster, clam, or 

 mussel, the shell must be opened before the food can be devoured. 

 But it is obvious that the strength exerted by the tube-feet of 

 the starfish will have little immediate effect on the powerful 

 muscles which hold together, and close tightly, the two valves 

 of a large oyster or quahog. Many theories have been proposed 

 in the attempt to explain the process by which these mollusks 

 are opened by the starfish. It was formerly thought that the 

 starfish excreted a poison which found its way between the 

 valves of the shell and finally stupefied the mollusk suffiqiently 

 for the valves to gape and allow the starfish to insert its stomach. 



