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Inside the membrane that surrounds the ovum, the stem-cell of the Ascidia, after fecundation, passes through just the same metamorphoses as the stem-cell of the Amphioxus. It undergoes total segmentation; it divides into two, four, eight, sixteen, thirty-two cells, and so on. By continued total cleavage the morula, or mulberry-shaped cluster of cells, is formed.
In this way we get the spherical, mulberry-shaped body, which we call the morula. The segmentation of the Amphioxus is not entirely regular, as was supposed after the first observations of Kowalevsky . It is not completely equal, but a little unequal.
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