. Cyclopedia of farm animals. Domestic animals; Animal products. SHELL-FISH SHELL-FISH 637 ized within a few minutes after reaching the sperm- atized water, and development follows rapidly and normally at temperatures between 60° and 85,° the optimum lying between 68° and 78°. In five to seven hours the egg has completed its segmentation and becomes a ciliated, free-swimming larva in the gastrula stage. It is scarcely larger than the egg, and has a ciliated stomach cavity less than one two-thousandth of an inch in diameter, so the food consists of only the minutest of alga; spores and microbes
. Cyclopedia of farm animals. Domestic animals; Animal products. SHELL-FISH SHELL-FISH 637 ized within a few minutes after reaching the sperm- atized water, and development follows rapidly and normally at temperatures between 60° and 85,° the optimum lying between 68° and 78°. In five to seven hours the egg has completed its segmentation and becomes a ciliated, free-swimming larva in the gastrula stage. It is scarcely larger than the egg, and has a ciliated stomach cavity less than one two-thousandth of an inch in diameter, so the food consists of only the minutest of alga; spores and microbes. Growth is slow at first, but the mantle- folds are formed, and the primitive shell secreted by the end of the first day. The valves are alike, resembling those of a clam. The embryos may now be called oyster " ; They swim awkwardly by means of a ciliated velar disk protruding between the valves. They are distributed by means of tidal currents, their limited swimming powers being used at first to change their vertical distribution while floating, and finally to secure a location on an object suitable for their attachment. Such objects are called clutch or collectors, and consist of the shells of oysters and other shell-fish, dead or living; but grass, bushes, trees, posts, rocks, peb- bles, pieces of crockery, glass, bricks, boats, leather and rubber boots are readily utilized. The clutch must be clean, not coated with slime, for the fry at this time are each less than one one-hundredth of an inch in diameter. After fixation, the baby oyster is called spat. The length of time the fry swims free has been variously stated as being from one to seven days, depending on temperature and food conditions, but it is certainly not shorter than five days, and often more than seven. Attachment is made by the left mantle edge, and growth is so rapid that the spat becomes visible to the naked eye within three days. Young oysters reach an inch in diameter in two months, and
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Keywords: ., bookauthorbaileylh, bookcentury1900, bookdecade1920, bookyear1922
