UTOBR.] LIFE-niSTOKY OP THE OYSTER. 331 



The sandy beaches of our coast are unfavorable in many places for 

 the growth of oysters, although many important beds exist on our 

 Atlantic coasts in favorable localities. 



The water in which oysters exist may be almost entirely fresh, and it 

 is doubtless a fact that in some cases, the water passing over the beds 

 in certain situations at ebb tide, as in rivers, may be absolutely fresh, a 

 fact noted by Semper in regard to the oysters of the Cumalaran Eiver, 

 at Basilan, south of Mindanao, in the East Indies. The hydrometer, in 

 some places where there are extensive beds in the Chesapeake, stands 

 at 1.007, and ranges on up to about 1.020 at the mouth of the bay, but in 

 places still higher up the bay than that where our lowest hydrometric 

 observation was made, the S])ecific gravity of the water must be even 

 very much less, so that in such places where fresh water is received 

 from considerable streams from the land, and where oysters are known 

 to exist, the water must often be almost or altogether fresh for hours 

 together. The precise degree of saltness of the water most favorable 

 to tlie growth of the oyster has not been determined, but to judge from 

 the circumstance that most of the oysters which go to supply our mar- 

 kets come from the great bays, rivers, and estuarine tributaries of the 

 coast it is fair to infer that such waters, which almost always have a 

 less specific gravity than those of the open sea, are the natural home of 

 this moUusk. 



American as well as the European oysters sometimes acquire a pe- 

 culiar greenish color in certain parts of the body, especially the gills 

 and ventricle of the heart. These are always tne first to be affected. 

 A very careful investigation made by the writer has resulted in show- 

 ing that it is the minute blood-cells which become tinged with a green 

 coloring matter, and that they then tend to lodge in the heart and gills 

 in great numbers, thus giving rise to the green appearance. The col- 

 oring matter, whatever it may be, is harmless, as it has never been 

 shown that it is a poisonous compound of copper, as has been errone- 

 ously supposed. It is very possibly derived from some vegetable color- 

 ing principle taken with the food, or it may possibly be an abnormal 

 product of the digestive process. It is equally certain that this green 

 coloration is not due to the presence of a vegetable parasite. 



Recent experiments have tended to show that it is not improbable that 

 both the American aud Portuguese oysters may be reared in very much 

 the same way as fish are bred from their ova. The experiments of M, 

 Bouchon-Brandely, in France, and of Colonel McDonald and the writer, 

 in this country, show that such a method is probably feasible. The 

 writer has shown that the eggs may be very expeditiously extracted 

 from the oyster somewhat after the method employed in taking the ova 

 from fishes. He has also devised a method of distinguishing the sexes 

 apart, so simple that the distinction may be made without even the 

 use of a pocket lens. The eggs and milt after the removal from the 

 parent animals, may be poured together, in order that fertilization may 



