Spiral cleavage is characteristic of protostomes. A developing embryo has spiral cleavage if as it undergoes cell division (cleavage) and changes from a four-cell embryo to an eight-cell embryo, the cells divide at sli ght angles to one another, so that the none of the four cells in one plane of the eight-cell stage is directly over a cell in the other plane.

Radial cleavage is characteristic of deuterostomes. A developing embryo has radial cleavage if as it undergoes cell division (cleavage) and changes from a four-cell embryo to an eight-cell embryo, the cells divide such that each cell in the top four cell plane is directly over one other cell in the bottom plane.

The two forms of cleavage are diagrammed here:

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