Dictionary.net

A naked cell, devoid of membrane ; the first or single-cell stage of an embryo ; the internal-bud stage in the life-history of Neosporidia.

[Greek] A naked cell, devoid of membrane; the first or single-cell stage of an embryo; the internal-bud stage in the life-history of Neosporidia (zool.).

A mass having the attributes of a cell, but with no investing membrane; also a cell exclusive of the cell wall.

Of Villot, the nucleus of the ovum. [Gr.]