FISHERIES OF THE UNITED STATES. [58] 



The animals grow very rapidly, attaining maturity in one season. 

 The young are produced in May and in the summer months, and during 

 the early stages of development are free-swimming. While embryonic, 

 they have organs both of sight and hearing, and are also provided with 

 a "foot"; but as they develop, their powers of sight and swimming 

 are lost. When they finally locate themselves they are about the size 

 of the head of a pin, but this size rapidly increases. The destructive 

 powers of the "ship-worm" are well known, and probably there is no 

 effective remedy except that in use for protecting the bottom of vessels, 

 viz., copper sheathing. The various poisonous substances applied to 

 timber are of no use, as the animal does not live on the wood, but uses 

 it as a location only. The only remedies likely to succeed are those 

 which will prevent an entrance. The United States Engineer Corps 

 has experimented, at the Delaware Breakwater, for some years, with 

 wood that had been treated with creosote, and the experiments appear 

 to have been successful; but whether the success is accidental or not 

 has not yet been determined. 



Martesia cuneiformis, Gray. 



This is another species of the genus Pholas, and is known as the " Bor- 

 ing Pholad," of the oyster-beds. It is very common and abundant in 

 Chesapeake Bay, and is found in any waters to which Chesapeake oys- 

 ters have been transported. It lives in small chambers, wliich it exca- 

 vates in the shells of oysters or other bivalves, but rarely does any 

 serious damage, the efforts of both oyster and pholad being directed to 

 the prevention of complete penetration of the valve. The pholad ap- 

 pears to flourish best in brackish water, and in Chesapeake Bay was most 

 abundant on oyster-beds that had evidently deteriorated. Their pres- 

 ence, therefore, in large numbers is considered to be one of the indica- 

 tions of deterioration. 



