. The biology of the frog . H Fig. 17.— Segmentation of the egg and formation of the blastopore. A,eight-cell stage seen from one side; />, beginning of sixteen-cell stage;C, thirtv-two-cell stage; D, forty-eight-cell stage; E, F, and G, succes-sive later stages of cleavage; H, beginning of the blastopore in the formof a small crescent; /, circular blastopore on the vegetative side of theegg. (After Morgan.) v THE DEVELOPMENT OF THE FROG 93 segmentation the cells are much larger at the vegetative poleand gradually become smaller toward the opposite side ofthe egg. In the first few cleavages
. The biology of the frog . H Fig. 17.— Segmentation of the egg and formation of the blastopore. A,eight-cell stage seen from one side; />, beginning of sixteen-cell stage;C, thirtv-two-cell stage; D, forty-eight-cell stage; E, F, and G, succes-sive later stages of cleavage; H, beginning of the blastopore in the formof a small crescent; /, circular blastopore on the vegetative side of theegg. (After Morgan.) v THE DEVELOPMENT OF THE FROG 93 segmentation the cells are much larger at the vegetative poleand gradually become smaller toward the opposite side ofthe egg. In the first few cleavages the planes of division lieat right angles to the surface of the egg, but subsequentlyplanes of division occur parallel to the surface, so that the eggcomes to consist of more than one laver of cells in thickness.
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