from the GNU version of the Collaborative International Dictionary of English

  • n. A primeval larval form; a double-walled sac from which, according to the hypothesis of Haeckel, man and all other animals, that in the first stages of their individual evolution pass through a two-layered structural stage, or gastrula form, must have descended. This idea constitutes the Gastræa theory of Haeckel. See gastrula.

from The Century Dictionary and Cyclopedia

  • n. In biology, a hypothetical animal form assumed by Haeckel as the ancestor of all metazoic animals — that is, of those which pass through or attain to the morphological form of a gastrula. See gastrula.


Sorry, no etymologies found.


  • We shall make use of it later on for our monophyletic theory of descent -- the hypothesis of a common descent of man and all the metazoa from the gastraea.

    The Evolution of Man — Volume 1

  • The gastraea theory shows us how to do this, by representing the embryology of the lowest vertebrate, the skull-less amphioxus, as the original form, and deducing from it, through a series of gradual modifications, the gastrulation and coelomation of the craniota.

    The Evolution of Man — Volume 1

  • Hence in the light of the gastraea theory we must regard the features of the amphioxus as the only and real primitive structure among all the vertebrates, departing very little from the palingenetic embryonic form.

    The Evolution of Man — Volume 1

  • In the light of the gastraea theory it is hardly necessary to dwell on the defects of this earlier view and the erroneous conclusions drawn from it.

    The Evolution of Man — Volume 1

  • The gastraea theory, which has its chief application here, teaches us that it is the very reverse of the truth.

    The Evolution of Man — Volume 1

  • Just as the gastraea-theory explains the origin and identity of the two primary layers, so the coelom-theory explains those of the four secondary layers.

    The Evolution of Man — Volume 1

  • As this theory, a logical conclusion from the gastraea theory, has been fully substantiated by the comparative study of gastrulation in the last few decades, we must exactly reverse the hitherto prevalent mode of treatment.

    The Evolution of Man — Volume 1

  • According to this gastraea-theory there was originally in all the multicellular animals ONE ORGAN with the same structure and function.

    The Evolution of Man — Volume 1

  • Finally, I discovered them (1872) in the lowest tissue-forming animals, the sponges, and proved in my gastraea theory that these two layers must be regarded as identical throughout the animal world, from the sponges and corals to the insects and vertebrates, including man.

    The Evolution of Man — Volume 1

  • Even then the egg was first a gastraea-egg, then a platode-egg, then a vermalia-egg, and chordonia-egg; later still acrania-egg, then fish-egg, amphibia-egg, reptile-egg, and finally bird's egg.

    The Evolution of Man — Volume 2


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