THE OYSTER AND THE OYSTEE INDUSTRY. 



19 



the bottom, «nd occasionally they freeze fast to the underside of 

 the ice and are carried away when it floats. 



FOOD OF THE OYSTER. 



The food of the oyster consists of microscopic plants and animals 

 and organic detritus growing or found in the water on and above 

 the bottoms on which the oysters lie, or carried to such waters 

 by currents. 



A large proportion of the oyster's food is made up of the plant 

 forms which are known as diatoms. There are many 'species of 

 diatoms, typical forms being shown in text figure 2. Diatoms are 

 found in more or less abundance in almost all waters, varying greatly 



Fig. 2. — Typical diatoms, which make up a large part of the food of the oyster . Magnified about 500 times. 



(After Moore ) 



in numbers in different places and at dift'erent seasons in the same 

 place or in the same season of different years. 



Diatoms derive their sustenance from the various organic mate- 

 rials washed down from the land and held in solution in the water. 

 These organic fertilizers consist of decayed and decaying vegetable 

 and animal matter gathered up from the land by the water result- 

 ing from rains and carried down streams and rivei's to the sea. The 

 food supply of oysters is thus directly affected by the character of 

 the soil adjoining the tributaries leading to the water over the beds, 

 by the kind and amount of forest or other vegetation and animal 

 life on that soil, by the industries carried on there, and by the amount 

 and seasons of rainfall. 



While a large portion of the food of the oyster is made up of 

 diatoms, considerable numbers of microscopic animal forms are 

 35286°— 21 22 



