Conditions Governing Oyster Growth 95 



be driven into it, by force of hand alone, to a depth of 

 several feet. It is very generally believed that such con- 

 ditions cannot be overcome, the assumption being that 

 any kind of pavement placed on it would sink below the 

 surface. That such is not true, will be shown in the 

 discussion of the Louisiana field. In parts of Long 

 Island Sound, where mud is deep but not so soft as in 

 the Gulf, bottoms have been successfully prepared by 

 paving with shells or with sand and gravel. Bottoms 

 naturally sandy are also often selected by the oyster 

 farmer, but under shallow water, where they may be 

 shifted by wave action, they are unsafe. It is specially 

 desirable that the bottom should be firm, to withstand 

 wave or tide action where spat is to be gathered on col- 

 lectors, for the young are quickly smothered in a quan- 

 tity of mud that would not seriously affect mature 

 oysters. 



The oyster finds almost its entire food supply in 

 diatoms of various species. These are floating plants, 

 microscopically small, which derive their nourishment 

 from substances brought down in solution from the land. 

 Their distribution along the coast is universal. They are 

 not confined to the surface, but may be found at all 

 depths. Every one has noticed the brown coat left on 

 the surface of a clam flat when it is exposed at low 

 water. When examined, this is found to contain vast 

 numbers of diatoms, though it is not by any means en- 

 tirely or even chiefly composed of them, as sometimes 

 stated. 



The amount of available oyster food over a given area 

 depends largely on water currents. Where there is no 

 current, oysters quickly exhaust the water about them 

 of the food that it carries. A current continuallv re- 



