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
The embryo in its period of most active morphogenetic movements is usually called a gastrula, but as all agree this word has no morphologic meaning anymore.
The young amphioxus has, at this stage, which is called the gastrula stage, a curious parallelism with such a lowly form as the
This stage is called the gastrula stage; ar. is the cavity of the gastrula, the archenteron; b.p. is its opening or blastopore.
I conceived the embryonic form, in which the whole structure consists of only two layers of cells, and is known as the gastrula, to be the ontogenetic recapitulation, maintained by tenacious heredity, of a primitive common progenitor of all the Metazoa, the Gastraea.
The typical embryonic form of the metazoa, as it is presented for a time by this simple structure of the two-layered body, is called the gastrula; it is to be conceived as the hereditary reproduction of some primitive common ancestor of the metazoa, which we call the gastraea.
As we saw, the original, palingenetic form of the gastrula is a round or oval uni-axial body, the simple cavity of which (the primitive gut) has an aperture at one pole of its axis (the primitive mouth).
The ovum is now what has been called a gastrula; and it is of importance to observe that probably all the Metazoa pass through this stage.
All I could find about this enigmatic term was some World of Warcraft guy, and some scientific stuff about the embryonic phase of an animal preceding the "gastrula" phase.
Haeckel maintained that the "gastrula" stage occurred in the development of all Metazoa, and that it was typically formed, by invagination, from
We have already pointed out (Chapter 1.9) how the epigastrula of the mammals (Figure 1.67) can be reduced to the original type of the bell-gastrula, which is now preserved by the amphioxus alone (Figure