38 THE OYSTER. 



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

 pair of fleshy organs, Plates I and II, w, 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 

 cilia 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- 

 tine, and dark-colored liver, as these will be under- 

 stood from the figure. The chief purpose of this 

 anatomical sketch is to show the wonderful way in 

 which the gills of the oyster fit it for gathering up the 

 microscopic life of our bay, and for turning it into 

 valuable human food. Looked at from this point of 

 view, the minute anatomy of the animal becomes emi- 

 nently practical, as it enables us to understand its true 

 relation to man. 



In view of the very exceptional fertility of the bay, 

 and its boundless capacity for producing microscopic 

 vegetation, the immense importance of an animated 

 strainer perfectly adapted for filtering very great 

 quantities of water, for gathering up the microscopic 

 life which it contains, for digesting and assimilating 

 it, and for converting it into food of the most attractive 



