protembryo

from The Century Dictionary.

• noun A stage of the ova of metazoic animals which is parallel with the adult colonies of certain protozoans: the monoplast of Lankester, or amphimorula of Haeckel, including the monoplacula and diploplacula of Hyatt.
• noun A term applied to the ovum and its cleavage stages in the development of a polyzoan.