from
The Collaborative International Dictionary of English v.0.48
Zona \Zo"na\, n.; pl. {Zonae}. [L., a girdle. See {Zone}.]
A zone or band; a layer.
[1913 Webster]
{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.
[1913 Webster]