40 THE OYSTER. 



oyster must strain many gallons of water to get its 

 daily bread ; but the gills, with their hundreds of thou- 

 sands of microscopic water pores, are most efficient 

 strainers. 



The surface of the gills is covered by an adhesive 

 excretion, for entangling the microscopic organisms 

 contained in the water, and as this circulates over and 

 through the gills, they stick fast like flies on fly-paper. 

 The hairs which drive the water through the gills, push 

 the slime, with the food which has become entangled 

 in it, towards the mouth, which is well up towards the 

 hinge ; for it is hardly necessary to say that what the 

 oystermen call the mouth is only the opening between 

 the halves of the mantle. 



On each side of the mouth, Plate II, m, there is a 

 pair of fleshy organs, Plate I and II, h, called the 

 lips, although they are more like mustaches than lips, 

 for they hang down on each side of the mouth. One 

 on the right is joined to one on the left, above the 

 mouth, while the other two are joined below it, so that 

 the mouth itself lies in a deep groove or slit between 

 the lips. 



The ends of the gills fit into this groove, and as the 

 hairs slide the food forward, it slips at last between the 

 lips and slides into the mouth, which is always open. 

 As this process is going on whenever the oyster is 

 breathing, the supply of food is continuous, and while 

 it consists, for the most part, of invisible organisms, 

 the oyster's stomach is usually well filled. It is not 

 necessary to describe the oyster's stomach and intes- 



