1. 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 Gastraea theory of Haeckel. See Gastrula.
Origin: NL, from Gr, the stomach.
Source: Websters Dictionary
(01 Mar 1998)
