• WordNet 3.6
    • n gastrula 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
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Webster's Revised Unabridged Dictionary
    • n Gastrula (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 Gastræa.
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Century Dictionary and Cyclopedia
    • n gastrula In embryology, that form of the germ of the Metazoa which is a germcup of which the walls consist of two layers.
    • n gastrula 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.
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Chambers's Twentieth Century Dictionary
    • n Gastrula that embryonic form of metazoic animals which consists of a two-layered sac enclosing a central cavity and having an opening at one end:—pl. Gras′trulæ
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Webster's Revised Unabridged Dictionary
NL., dim. fr. Gr. the stomach


In literature:

This cup-shaped embryo is called the gastrula.
"The Whence and the Whither of Man" by John Mason Tyler
The gastrula stage was the palingenetic repetition of the ancestral form of all Metazoa, the Gastraea.
"Form and Function" by E. S. (Edward Stuart) Russell
With what lower type has the gastrula been compared?
"Text Book of Biology, Part 1: Vertebrata" by H. G. Wells
Gastrula: that embryonic stage resembling a sac, with an outer layer of epiblastic cells and an inner layer of hypoblastic cells.
"Explanation of Terms Used in Entomology" by John. B. Smith
The segmentation is complete; one side of the hollow blastosphere invaginates and forms a gastrula.
"Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 7" by Various
Is there any considerable difference between the size of the egg and the size of the blastula and gastrula?
"A Guide for the Study of Animals" by Worrallo Whitney
The embryo in this stage is known as a gastrula.
"The Biological Problem of To-day" by Oscar Hertwig
A gastrula is established by a mixed process of embole and epibole.
"Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7" by Various
The development of the Lancelet presents us with an instance of the two-layered larva, or Gastrula.
"Stories of the Universe: Animal Life" by B. Lindsay
From the gastrula type the higher subdivisions of animal life probably diverged, as separate branches from a common trunk.
"The Elements of Geology" by William Harmon Norton