Gastraea
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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 atwo-layered structural stage, or gastrula form, must have descended.This idea constitutes the Gastræa theory of Haeckel. See Gastrula.
Gastraea meaning & definition 1 of Gastraea.