Egg

Reproductive cell of a female organism. It differ from the male germ-cell in being non-motile and in having much greater size, due mainly to the quantity of yolk stored up in it as food for the embryo. Reptiles and birds add a layer of "white" or albumen around the true egg ("yolk") and inclose the whole by a porous shell of lime salts, overlying two membranes between which, at the large end, an air space forms as the fluids evaporate or the contents are used by the developing young. The Mammalian egg having no "white" and little yolk is of microscopic size, except in the DUCK-MOLE (q.v.). The eggs of many of the Insects (Plant-lice) and Crustacea ( Daphnia ), etc., can develop without being impregnated; such eggs are "parthenogenetic." The female oyster may spawn as many as fifty million eggs in one season. This great number is required because of the small chance there is of impregnation occurring in the environing water. For a similar reason most fishes have great numbers of eggs. The amount of eggs used in the arts withdraw a large amount of food from the market. Egg albumen is used by calico printers for fixing better and lighter sorts of colors. It is also used for photographer's paper and for clarifying vinous and syrupy liquors, for upon being heated it coagulates and envelops the substances which it is desired to remove. The yolk is used in an emulsion for tanning leather used in the manufacture of kid gloves; the yolk acting by the oil it contains, this oil giving the leather supplene and softne .