FURCULA.—The forked bone formed by the union of the collar-bones in many birds, such as the common Fowl.
GALLINACEOUS BIRDS.—An order of birds of which the common Fowl, Turkey, and Pheasant, are well-known examples.
GALLUS.—The genus of birds which includes the common Fowl.
GANGLION.—A swelling or knot from which nerves are given off as from a centre.
GANOID FISHES.—Fishes covered with peculiar enamelled bony scales. Most of them are extinct.
GERMINAL VESICLE.—A minute vesicle in the eggs of animals, from which the development of the embryo proceeds.
GLACIAL PERIOD.—A period of great cold and of enormous extension of ice upon the surface of the earth. It is believed that glacial periods have occurred repeatedly during the geological history of the earth, but the term is generally applied to the close of the Tertiary epoch, when nearly the whole of Europe was subjected to an arctic climate.
GLAND.—An organ which secretes or separates some peculiar product from the blood or sap of animals or plants.
GLOTTIS.—The opening of the windpipe into the œsophagus or gullet.
GNEISS.—A rock approaching granite in composition, but more or less laminated, and really produced by the alteration of a sedimentary deposit after its consolidation.