It appears, from the experience of one of the most enthusiastic of French oyster-growers (Dr. Kemmerer), that oysters _grow_ best in muddy water, and _breed_ best in clear water. Thus the open sea is the place where the spat should fall and be secured, and, as soon as it is of a suitable size, it should be transferred to the closed tank or reservoir, where it will find the quiet and the food (confervae, infusoria, minute algae) which are so requisite for its proper growth. In muddy ground the animal and phosphorous matter increases, and the flesh becomes fatter and more oily. A sudden change from the clear sea-water to the muddy tank is inadvisable, and thus a series of shiftings through tanks with water of graduated degrees of nourishment is the secret of proper oyster cultivation. The American oyster trade is larger even than the French. The Baltimore oyster beds in the Chesapeake River and its tributaries cover 3000 acres, and produce an annual crop of 25 million bushels, as many as 100,000 bushels being sometimes taken from Chesapeake Bay in a single day. Baltimore is the centre of the tinned oyster trade, while that in raw oysters centres in New York. Most of the beds whose produce is carried to New York are situated in New Jersey, Connecticut, Delaware, or Virginia. The laws of these states do not allow the beds to be owned by any but resident owners, and the New York dealers have consequently to form fictitious partnerships with residents near the various oyster beds, supply them with money to buy the beds and plant the oysters, and then give them a share in the profits. It has been estimated that from the Virginia beds 4,000,000 bushels of oysters are carried every year to Fair Haven in New England, 4,000,000 to New York, 3,000,000 to Providence, and 2,000,000 each to Boston, Philadelphia, and Baltimore. The American ‘native’ (_O. virginica_) is a distinct species from our own, being much larger and longer in proportion to its breadth; it is said to be also much more prolific. According to Milne-Edwards,[222] in the great oyster parks on the coasts of Calvados, the oysters are educated to keep their shells closed when out of water, and so retain water enough inside to keep their gills moist, and arrive at their destination in good condition. As soon as an oyster is taken out of the sea, it closes its shells, and keeps them closed until the shock of removal has passed away, or perhaps until the desirability of a fresh supply of water suggests itself. The men take advantage of this to exercise the oysters, removing them from the sea for longer and longer periods. In time this has the desired effect; the well-educated mollusc learns that it is hopeless to ‘open’ when out of the water, and so keeps his shell closed and his gills moist, and his general economy in good condition.