12:i 



SEA-SHOKE LIFE 



Fig. Xo: AMElifC'AX ciYSTEIi. 



of tlie body, as two sheets on each side, near the mid-dorsal line, 

 and which lie free in the space lietween the mantle and the body 



of the oyster. The digestive tract is 

 mucli coiled and twisted, and the mouth 

 of the oyster is placed close to the 

 hinge at the narrow apex of the shell, 

 where it is surrounded by curtain-like 

 lips. 



There is a well developed stomach 

 which often contains a glistening, gela- 

 tinoas, rod called the "crystalline style." 

 The function of this is unknown, al- 

 though it may possibly rejn-esent stored 

 up nutrient material. 



The large green-colored liver sur- 



ronnds the stomach into which it 



empties, while the reproductive organs 



surround the coiled intestine, and are verj' large during the 



warmer months when the o\'sters are spawning. 



A full-grown female oyster will produce about 9,000,000 eggs, 

 each being about one-five-hundredth of an inch in diameter. The 

 eggs are cast out into the water through tlie oviducts Avliich open 

 into the gill cavity on both sides of the body below the adductor 

 muscle. They then develop into little free-swimming larvas which 

 swim rapidly through the water by means of their Iiair-like cilia. 

 The shells then apjDcar upon the sides of the body, and when about 

 one-eighth of an inch wide the creature settles to the bottom with 

 its left side down, and there remains throughout life. 



The true lieart of the oyster is bull)-like in shape, and lies 

 within a delicate translucent sac close to the inner side of the great 

 adductor muscle. It pulsates slowly, and pumps blood from the 

 gills to other parts of the body. Growth is rapid at first, for 

 under fav'orable conditions the little oyster, or "spat," as it is 

 called, may Ijecome an inch across its shell in seven weeks, and 

 two inches in three months. 



The oysters feed upon a great variety of minute oi-ganisms, 

 such as simple unicellular plants and animals, and small marine 

 larvie. The gills are covered with waving cilia, which create a 



