n. [ Gr. blasto`s sprout + E. derm. ] (Embryology) the early stage of an embryo after the first cleavages of the ovum; also, the layer of cells of which the early embryo is composed; specifically: (a) the early embryo developing from a blastodisc, after the blastocoel has formed. (b) in an insect embryo, the layer of cells that surrounds the internal mass of the yolk. [ PJC ]

{ } a. Of or pertaining to the blastoderm. [ 1913 Webster ]