Before this period of its life arrives, however, many are the dangers to which it is exposed: its enemies are numerous; they lie in ambush for it in every cranny! It has to guard itself against eddies and currents, which would drive it out to sea, and mud banks, in which it would be smothered. Crustaceans, worms, and polyps, with other equally voracious marine inhabitants, prey upon it. Last, but not least, come the terrible and multiplied engines of the eager fisherman—and we readily comprehend why the oyster is provided with such accumulated masses of ova.
If the young bivalve is fortunate enough to escape all the snares and dangers we have enumerated, it grows rapidly. It is quite microscopic at the period of its discharge from the parent shell; at one month it is of the size of a large pea, at the end of six months it is about three-quarters of an inch, a year after its birth an inch and a half to two inches, and finally, at the end of three years it has become merchandise; that is to say, it is in a state to be sent to the parks for preservation and feeding. In Fig. 171 we see a group of oysters,[9] of various ages, attached to a piece of wood: a being oysters of twelve to fifteen months, b five or six months, c three to four months, d one to two months, and e oysters twenty days after birth.
Fig. 171. Groups of Oysters of different ages attached to a block of wood.
The species of oysters usually eaten are the common oyster (Ostrea edulis, Linn.) of our own coasts and the opposite shore, and the horsefoot oyster (O. hippopus, Linn.). On the Mediterranean coast are the rose-coloured oyster (O. rosacea, Favanue), and the milky oyster (O. lacteola, Moquin-Tandon), besides the small and little-known crested oyster (O. cristata, Born), and the folded oyster (O. plicata, Chemnitz). On the Corsican coast is the oyster called foliate (O. lamellosa, Brocchi).
There are two principal varieties of the common oyster dredged on the French coast, which differ in size and delicacy of flavour. These are the Cancale and Ostend oyster. When the first has been fed for some time in the oyster park, and has assumed its greenish hue, it is designated the Marenna oyster, from "the park" so named in the Bay of Seudre. Of this green colour we shall speak elsewhere.
Who believed Uncle Jack when he told us in our youth of oysters growing on trees, and oysters so large that they required to be carved like a round of beef—of oysters on the Coromandel coast as large as soup-plates? Nevertheless Uncle Jack's stories were true: there are oysters which require carving, and oysters have been plucked off trees. In some parts of America they grow very large. Virginia possesses nearly two million acres of oyster-beds. The sea-board of Georgia is famed for its immense supplies; the whole coast of Long Island, extending to a hundred and fifteen miles, is occupied with them, and all over the States evidence is to be seen of the estimate in which the favoured bivalve is held by the American people.
Natural oyster-beds are found in bays, estuaries, and other sheltered sinuosities of the coast, with shelving and not too rocky bottoms, such places being, according to the natural law of production, favourable for the increase of the colony. Such banks abound in every sea. In France the oyster-beds of Rochelle, of Rochefort, the Isles of Ré and Oleron, the Bay of St. Brieuc, of Cancale, and Granville, are famous for the quality of their produce.
On the Danish coast there are from forty to fifty oyster-banks, situated on the west coast of Schleswig; the best bed lying between the small isles of Sylt, Amron, Fohr, Pelworm, and Nordstrand. At the point of Jutland, and opposite Shagen, beds less productive are found.
The great oyster-beds of England extend from Gravesend, in the estuary of the Thames and Medway, along the Kentish coast on the one hand, and the estuary of the Colne and other rivers on the Essex coast. The Frith of Forth is also famous for its oyster-beds, extending from Preston Pans far up the estuary of the river; but, curiously enough, all these great banks, without exception, have been impoverished, and all but exhausted, by improvident dredging, in spite of the "close season" which has always existed.[10]