"Gastrulation of an Ascidian. I. Vesicular Morula of an Ascidian flattened and about to undergo gastrulation. II. Gastrulation effected. fh, cavity of the morula, or blasto-invagination; ch, dd, large blastomeres of the hypoblast, inclosed in small blastomeres of the epiblast." -Whitney, 1911

Sea Squirt Gastrulation

"Gastrulation of an Ascidian. I. Vesicular Morula of an Ascidian flattened and about to undergo gastrulation.…