50 BULLETIN OF THE NATURAL HISTORY SOCIETY. 



Economics. Of all invertebrate animals that live in the- 

 sea, perhaps of all invertebrate animals whatever, the Oyster 

 is far the best known. It is very widely distributed, occurring 

 in nearly all the seas of the globe, and there are some seventy 

 species recognized. Howfar back dates its use by man we cannot 

 say, but the shells are found in very ancient kitchen-middens 

 or refuse heaps in America, and still more ancient ones in 

 Europe. This rather throws doubt upon the story sometimes 

 told that their excellence was first made known by an inquisi- 

 tive walker on the seashore whose finger was pinched by one 

 and carried for relief to his mouth, T':e historical accuracy 

 of this tale is still further impugned by the fact that the same 

 is told of the origin of several other excellent edibles. 



That the Oyster is a nutritious and otherwise good article 

 of food, all physicians, chemists and human experience agree. 

 A discussion of its value compared with other food substances 

 will be found in the introductory part of this paper (p. 9). 

 It must be remembered that those tables express merely the 

 absolute nutritive value of the various substances, and give no- 

 indication of the relative digestibility and other differences 

 which give this Mollusc its chief value. 



Though persons are occasionally found (of whom the 

 writer is one), who dislike Oysters, we have never heard of 

 any cases of actual poisoning by them. It is sometimes 

 thought that those which have the gills of a green color are 

 injurious, but repeated chemical analysis and careful experi- 

 ments have shown that they are quite harmless. The green 

 color is due to a pigment absorbed from their food, which, in 

 such cases, consists chiefly of a particular kind of Diatoms. 

 By feeding them other food for a time, their white color 

 returns, and vice versa, by feeding white Oysters on these 

 Diatoms they turn green. Indeed the epicures of Europe 

 esteem the green more highly than the white, and in France 

 there are beds in which they are carefully fed to make them 

 green. 



The United States is the greatest Oyster-producing country 

 in the world. According to the census of 1880, this fishery is- 



