THE OYSTER. 



49 



in the water, while the egg is motionless and sinks to 

 the bottom as soon as it is set free. 



When the reproductive elements are fully ripe they 

 are discharged from the body into the cloacal chamber 

 of the mantle. The male cells are swept out into the 

 ocean by the current produced by the hairs on the gills. 

 As they contain no food, their power to live inde- 

 pendently is very limited, and all soon die except those 

 that come into contact with eggs. 



In the American oyster the eggs are swept out into 

 the water in the same way. The eggs of the European 

 oyster are much larger and heavier, and they fall into 

 the water tubes of the gills and lodge there. Here 

 they are exposed to the current of water which circu- 

 lates through the gills, and this current brings with it 

 some of the male cells which swim in the water around 

 the oyster-bed. As soon as one of them comes into 

 contact with an egg it fuses with it and loses its 

 individuality and is lost in the substance of the egg, 

 which is thus fertilized and at once begins its develop- 

 ment into a new oyster. 



There is no such provision for securing the fertili- 

 zation of the eggs of the American oyster. They are 

 thrown out into the water, like the male cells, to be 

 fertilized by accident, and while many of them meet 

 with male cells, innumerable multitudes sink to the 

 bottom and are lost. It is fortunate for other animals 

 that this is the case, for our oyster is so prolific that 

 if all the eggs were to be fertilized and were to live 

 and to grow to maturity, they would fill up the entire 



