Source : Webster's Revised Unabridged Dictionary (1913)

Blastosphere \Blas"to*sphere\, n. [Gr. blasto`s sprout + E.
   sphere.] (Biol.)
   The hollow globe or sphere formed by the arrangement of the
   blastomeres on the periphery of an impregnated ovum.

   Note: [See Illust. of {Invagination}.]

Source : WordNet®

blastosphere
     n : the blastula of mammals [syn: {blastocyst}]