Zo"na (?), n.; pl. Zonae (#). [L., a girdle. See Zone.]
A zone or band; a layer.
Zona pellucida. [NL.] Biol. (a) The outer transparent layer, or envelope, of the ovum. It is a more or less elastic membrane with radiating striae, and corresponds to the cell wall of an ordinary cell. See Ovum, and Illust. of Microscope. (b) The zona radiata. -- Zona radiata [NL.] Biol., a radiately striated membrane situated next the yolk of an ovum, or separated from it by a very delicate membrane only.
© Webster 1913.