THE OYSTER. 41 



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

 stood from the figure. The chief purpose of the 

 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 quan- 

 tities 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 

 and nutritious character, cannot be overestimated ; but 

 after we have studied the embryology of the oyster, 

 we shall understand why the natural oysters alone 

 can never utilize all the resources of our waters. We 

 shall see why it is that the oyster is so well fitted for 

 domestication and cultivation, and why the cultivation 

 of oysters will render the Chesapeake Bay incomparably 

 more valuable than it has ever been even before our 

 natural beds began to deteriorate. 



THE OYSTER AS A SOURCE OF THE INFECTION OF HUMAN 

 BEINGS WITH CHOLERA AND TYPHOID FEVER. 



The reader of the preceding pages will see that the 

 oyster is an admirably constructed machine for filtering 

 5 



