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Every human body begin as a single nucleated cell. This cell, known as the ovum, divides or segments and gives rise to a mass consisting of a number of similar units known as the morula. At this stage there are no distinguishable tissues.

Cell Development

Every human body begin as a single nucleated cell. This cell, known as the ovum, divides or segments…

"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.…