young inhabitant, which has every facility for the purpose: it is even said to swim about near the mother, before final dismissal from the maternal protection, seeking shelter at the least alarm between the valves of the parent shell. The pad disappears after the young oyster has finally attached itself to a permanent bed of its own. [Illustration: Fig. 170. Young Oysters furnished with locomotive organs.] 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. [Illustration: 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.