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"Gastrula of a Chalk-sponge (Olynthus). A, external view." -Whitney, 1911

Chalk Sponge Gastrula

"Gastrula of a Chalk-sponge (Olynthus). A, external view." -Whitney, 1911

"Gastrula of a Chalk-sponge (Olynthus). B, longitudinal section through the axis: g, primitive intestine; o, blastopore; i, inner cell-layer of the body-wall; e, outer cell-layer." -Whitney, 1911

Chalk Sponge Gastrula

"Gastrula of a Chalk-sponge (Olynthus). B, longitudinal section through the axis: g, primitive intestine;…