blastoderm

(blas’to-derm) [Gr. βλαστός germ + δέρμα skin]. The delicate membrane which lines the zona pellucid a of the impregnated ovum. The blastuderm is formed by the cells (basto meres) A tumor com- which result from the splitting up of the ovum after impregnation, and have been pushed from the center of the accumulation of the blastochyle. The blastoderm forms a hollow sphere (dlastodermic vesicle). tri laminar b., the stage of development in which the embryo is represented by the three primary layers: the ectoderm, the mesoderm, and the entoderm.