A hollow ball of
cells with one part of the ball pushed into the interior
blastocoele (called an
invagination). This early stage of animal
embryonic development forms just after the
blastula stage. By the end of the gastrulation process, the different
embryonic
germ layers (
endoderm,
ectoderm, and sometimes
mesoderm) can clearly be identified.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.