The Collaborative International Dictionary of English v.0.48:

Blastoderm \Blas"to*derm\, 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] Blastodermatic