Blastaea

a hypothetical ancestor of multicellular animals.

In the opinion of E. Haeckel, the blastaea was a globular organism that had an interior cavity and a walled body and consisted of a single layer of cells. Haeckel believed that colonial protozoa (Volvox, for example) were analogues of the blastaea. Proceeding from the position he had developed, that the organism in its individual development (ontogeny) briefly repeats the history of the development of the species (phylogeny), Haeckel believed that one of the stages in the development of the embryos of all multicellular animals (the blastula) is a repetition of the structure of the blastaea in ontogeny.