Gastraea

Like the latter, the human gastrula and that of all other mammals must be regarded as the ontogenetic reproduction of the phylogenetic form that we call the Gastraea, in which the whole body is nothing but a double-walled gastric sac.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

The undifferentiated skin-layer or ectoderm of the Gastraea is the simple stratum of cells from which the differentiated sense-organs of all the Metazoa

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

Haeckel, Professor Ernst. -- his Gastraea theory, dependent on Huxley's discoveries.

Life and Letters of Thomas Henry Huxley — Volume 3 Leonard Huxley 1896

I conceived the embryonic form, in which the whole structure consists of only two layers of cells, and is known as the gastrula, to be the ontogenetic recapitulation, maintained by tenacious heredity, of a primitive common progenitor of all the Metazoa, the Gastraea.

Evolution in Modern Thought Gustav Schwalbe 1880

I have pointed out in my Study of the Gastraea Theory [not translated] (1873) the important consequences of this conception in the morphology and classification of the animal world.

The Evolution of Man — Volume 1 Ernst Heinrich Philipp August Haeckel 1876

This two-layered embryonic form is the ontogenetic reproduction of the extremely important phylogenetic stem-form of all the Metazoa, which we have called the Gastraea.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

Monograph on the Sponges, and developed in the Study of the Gastraea

The Evolution of Man — Volume 1 Ernst Heinrich Philipp August Haeckel 1876

The Gastraea bilateralis, of which we may conceive the bilateral gastrula of the amphioxus to be a palingenetic reproduction, represented the two-sided organism of the earliest Metazoa in its simplest form.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

Although I laid special stress on the great morphological importance of this cavity in my Study of the Gastraea Theory, and endeavoured to prove the significance of the four secondary germinal layers in the organisation of the coelomaria, I was unable to deal satisfactorily with the difficult question of the mode of their origin.

The Evolution of Man — Volume 1 Ernst Heinrich Philipp August Haeckel 1876

As the human embryo passes through the gastrula-form like that of all the other Metazoa, we can trace its phylogenetic origin to the Gastraea.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876