To the primitive two-cell-layered form, the hypothetical ancestor of all Metazoa or Enterozoa, Haeckel gave the name Gastraea; the em- bryonic form which represents in the individual growth from the egg this ancestral condition he called a " gastrula."
- Trichoplax adhaerens, an organism considered, on the Gastraea-hypothesis, to be closely allied to the progenitors of the Platyelmia.
The Gastraea-hypothesis is founded on quite other considerations.
How would you define gastraea? Add your definition here.