(Biol.) A more or less spherical and transparent cell, which by a process of multiplication and growth develops into a mass of cells, constituting a new individual like the parent; an egg, spore, germ, or germ cell. Note: The ovum is a typical cell, with a cell wall, cell substance, nucleus, and nucleolus. In man and the higher animals the cell wall, a vertically striated membrane, is called the zona pellucida; the cell contents, the vitellus; the nucleus, the germinal vesicle; and the nucleolus, the germinal spot. The diameter of the ripe ovum in man and the domestic animals varies between 1-200 and 1-120 of an inch.
...