One of the most lucrative branches of foreign oyster-farming may be now described—_i.e._ the manufacture of the celebrated green oysters. The greening of oysters, many of which are brought from the Ile de Re parks, is extensively carried on at Marennes, on the banks of the river Seudre, and this particular branch of oyster industry, which extends for leagues along the river, and is also sanctioned by free grants from the state, has some features that are quite distinct from those we have been considering, as the green oyster is of considerably more value than the common white oyster. The peculiar colour and taste of the green oyster are imparted to it by the vegetable substances which grow in the beds where it is manipulated. This statement, however, is scarcely an answer to the question of “why,” or rather “how,” do the oysters become green? Some people maintain that the oyster green is a disease of the liver-complaint kind, whilst there are others who attribute the green colour to a parasite that overgrows the mollusc. But the mode of culture adopted is in itself a sufficient answer to the question. The industry carried on at Marennes consists chiefly of the fattening in claires, and the oysters operated upon are at one period of their lives as white as those which are grown at any other place; indeed it is only after being steeped for a year or two in the muddy ponds of the river Seudre that they attain their much-prized green hue. The enclosed ponds for the manufacture of these oysters—and, according to all epicurean authority, the green oyster becomes “_the_ oyster _par excellence_”—require to be watertight, for they are not submerged by the sea, except during very high tides. Each claire is about one hundred feet square. The walls for retaining the waters require therefore to be very strong; they are composed of low but broad banks of earth, five or six feet thick at the base and about three feet in height. These walls are also useful as forming a promenade on which the watchers or workers can walk to and fro and view the different ponds. The flood-gates for the admission of the tide require also to be thoroughly watertight and to fit with great precision, as the stock of oysters must always be kept covered with water; but a too frequent flow of the tide over the ponds is not desirable, hence the walls, which serve the double purpose of both keeping in and keeping out the water. A trench or ditch is cut in the inside of each pond for the better collection of the green slime left at each flow of the tide, and many tidal inundations are necessary before the claire is thoroughly prepared for the reception of its stock. When all these matters of construction and slime-collecting have been attended to, the oysters are then scattered over the ground, and left to fatten. When placed in these greening claires they are usually from twelve to sixteen months old, and they must remain for a period of two years at least before