FAMILY OSTFUEIDIE Genus OSTRIEA, Linn.
The Edible Oyster of Europe, (0. edulis, Linn.) is round in outline when young, but it becomes very much distorted as it grows. The concave left valve which is cemented to the sup port has marginal scallopings and shingled plaits or spines on the surface. The flat or concave right valve is smooth, as a rule. The individual is hermaphrodite, both male and female. Length. 3 to 6 inches.
Habitat.— Europe.
The Virginia Oyster (0. Virginica, Lister) is the North American species whose cultivation centres in Chesapeake Bay. Its form is irregular, elongated, with coarse, dingy exterior of limy shell layers, and polished but not pearly lining. The scar on each valve marks the place where the strong muscle is attached. Sexes distinct. Length, 6 to 15 inches.
Habitat.— Atlantic coast.
Some authorities recognise a second, deeply scalloped species. on northern shores, and designate it 0. borealis. In all proba bility it is but one form of the protean 0. Virginica.
423 The Oysters The growing oyster-beds about San Francisco Bay are stocked with 0. V irginica. "Seed" as large as a silver quarter is shipped in barrels across the continent, packed in damp seaweed. They illustrate the oyster's tenacity of life, for they live and grow and fatten for market. They spawn freely, but the young die, prob ably because the water is too cold.
The Lurid Oyster (0. lurida, Cpr.) a native of the Pacific coast, is small and has a thin purplish shell. It varies from round to oblong. I is flavour is indifferent. Length, 2 inches.
Habitat.— Pugent Sound to California.
The Tree or Coon Oysters (0. frons, Linn.) are found growing together, forming masses as big as a bushel basket hang ing from the supple aerial roots of the red mangrove in southern Florida, and built into the rocky breastworks of many a coral beach. They extend to North Carolina. The individual oysters
are small, with thick, rough, shapeless valves. It is surprising that it pays at all to open them. Yet I recall a most delectable stew made of this strange fruit of the mangrove tree. Raccoons feed upon them with avidity.
Of many species of oysters I make no mention. In spite of frills and plaits they are recognisable as oysters. The Chinese cultivate at least one species. There is a rumour of a Japanese oyster that measures a full yard in length. Its flesh is said to be disappointingly tough.
The Oyster's Anatomy.— The oyster is, to the average mind, a formless mass of succulent tissue, shaped by benign Providence to descend with ease "into the eager and expectant tomb." That is because anatomisation is a laboratory process, and we are accustomed to meet the oyster only at meal-time. As a living creature it is wonderfully made. Take a freshly-opened oyster of good size and examine it with care , you will soon forget that it is edible.
That enveloping web is the mantle; between the oyster and the shell this protecting garment lies'; its surface secretes the shell. See the cut stub of the adductor muscle in the middle of the body. By it the two shells were bound together in life. Lift the delicate mantle, and you see two thin, semi-circular leaves, free at their outer borders. These are the gills. Under them lies the central body mass; a second pair of gills is under it, and another mantle fold. On the hinge side of the muscle 424 The Oysters is the heart. In a live oyster you may see it beat! Forward of the gills are two small flaps, the palpi or lips. Between them the large mouth leads to the stomach and intestine. After wind ing through the body substance this alimentary tube ends in the mantle cavity just above and behind the adductor muscle. The dark mass surrounding the stomach is the liver. The kid neys and reproductive organs lie close to it, in the body mass.