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.

Gas"tru*la (?), n.; pl. Gastrulae (#) [NL., dim. fr. Gr. the stomach.] Biol.

An embryonic form having its origin in the invagination or pushing in of the wall of the planula or blastula (the blastosphere) on one side, thus giving rise to a double-walled sac, with one opening or mouth (the blastopore) which leads into the cavity (the archenteron) lined by the inner wall (the hypoblast). See Illust. under Invagination. In a more general sense, an ideal stage in embryonic development. See Gastraea.

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a.

Of or pertaining to a gastrula.

 

© Webster 1913.

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