Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. An embryo at the stage following the blastula, consisting of a hollow, two-layered sac of ectoderm and endoderm surrounding an archenteron that communicates with the exterior through the blastopore.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A stage in the development of embryos of most animals consisting of a two-layered sac of ectoderm and endoderm.

from the GNU version of the Collaborative International Dictionary of English

  • n. 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 gastræa.

from The Century Dictionary and Cyclopedia

  • n. In embryology, that form of the germ of the Metazoa which is a germcup of which the walls consist of two layers.
  • n. It is the result of that process of invagination which occurs in most animals, whereby a vesicular morula, blasto-sphere, or blastula is converted into a cup-like two-layered germ, with a blastopore or orifice of invagination, and an endoderm or membrane inclosing a primitive intestinal cavity, the endoderm itself being inclosed within an ectoderm. The word enters into many loose compounds of obvious meaning, as gastrula-body, -cup, -form, -formation, -germ, -mouth, -stage, -stomach, etc., mostly derived from the translation of the German compounds used in Haeckel's works. See gastrulation.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. double-walled stage of the embryo resulting from invagination of the blastula; the outer layer of cells is the ectoderm and the inner layer differentiates into the mesoderm and endoderm

Etymologies

New Latin : Greek gastēr, gastr-, belly + Latin -ula, feminine diminutive suff.
(American Heritage® Dictionary of the English Language, Fourth Edition)

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