MOLLUSCS. 259 



Mr. J. A. IJydei- solved tlie proWeiii in the- following inunner. An artificial pond was 

 formed, and filled with salt water, which was filtered througii sand, and all connection 

 with the ocean was by means of a ditch interrupted by a bank of sand. This permitted 

 a slight change of water with each tide, but prevented the entrance of injurious forms 

 and the exit of the young before their transformation into spat. In the pond were 

 [)laced numerous collectors, to which the spat could attach itself; and after the young 

 shells had attained sufficient size to take care of themselves, these collectors, with their 

 iriolluscan load, could be transferred to the beds in the adjacent sounds. By this 

 |ii-ocess the period of greatest mortality is ])assed in comparative safety, and the 

 result of Mr. Ryder's labors will doulifless lie to greatly increase tlic supplv of this 

 delicious bivalve. 



The oysters are taken from the be<ls by rakes, tongs, and dredges ; the names of 

 whitli indicate their general appearance. When brought to the shore, some are sent 

 lo market, while others are ' shocked,' and sold as solid meats. The extent of the 

 oyster industrj' in the United States can be seen from the following figures, extracted 

 IVoiri the census of 1880. The business gives employment to over fifty thousand per- 

 sons and over four thousand vessels, and involves an investment of over ten million 

 dollars. The number of bushels of oysters jiroduced is over twenty millions, and. at 

 first hand these sell for over thirteen millions of dollars. Each State has its own laws 

 and regulations regarding its shell-fisheries, and in Maryland and Virginia an (p\st(i- 

 ])olice is maintained, to prevent irregular fishing and depredations n|i(in the beds. 



Our east-coast oyster has been described under four specific names, rirf/iiiiaiia, vir- 

 ginica., borealis, and canadensis., but all have been shown to be varieties of one and 

 the same form. The average length of those brought to market is, ])erliaps, four to 

 six inches, but larger ones are not uncommon ; but how nmcli credence is to be given 

 to the following quotation from the "Mobile [Alal>ama] Uegister," of A])ril, 184(1, 

 taken from "Ingersoll's Monograph of the Oyster Industry,'' is a question. The quo- 

 tation runs : " The large oyster taken by Xavier Fran9ois, while oystering on Monday 

 last, was brought up from the wharf, on a Amy, last evening. An oyster measuring 

 three feet one inch in lengtli, and twenty-three and a half inclies across the widest 

 ])art of it, is a curiosity." 



On our western coast two species of oyster are eaten. Of these O. uonchophihi, 

 of California, is small, while the O. hirlda, from Shoalwater Bay, Washington Terri- 

 tory, is much larger and better. Still a large proportion of the trade is supplied by 

 oysters shipped from the Atlantic coast. In Eurojie the oysters most eaten are O. 

 (ingtdata and O. edulis. Of these the former has thi' sexes separate, while the latter 

 is herma])hrodite. Sjjace will not allow a detailed account of the many and successful 

 trials that have been made in the propagation of these forms, and we can only refer to 

 the green oysters so highly prized by the Parisian epicures. Many theories liave been 

 ]proposed to account for the color, — such as the presence of (^op]ier, etc., — but it now 

 seems probable that it is due to the effect of the food, tlie chlorophyl of the vegetable 

 food being transferred to the blood, or some peculiarity in other objects eaten affect- 

 ing the liver. The British market is now largely supplied from the United States, 

 the American oysters being much larger, and better flavored than those of European 

 seas. The trade amounts to alwut half a million dollars yearly. 



Edible oysters are found at the Cape of Good Hope, in Australia, .Ta])an, and else- 

 where. The O. faMemoanensis, of Ja])an, occasionally measures three feet in length. 

 Other forms which deserve mention are the species of the sub-genus Alectryonia, which 



