A hollow ball of cell
s 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 embryo
nic germ layer
, and sometimes mesoderm
) can clearly be identified.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.