Two-cell embryo. Coloured scanning electron micrograph of the blastomeres of a 2-cell embryo. The blastomeres (yellow) are the cells formed by the first division of the fertilized egg. They are either side of the plane of segmentation (vertical line). Most of the membranous envelope, the zona pellucida, which in life would surround the embryo has been destroyed in preparation. The only remaining piece of zona pellucida (pink) is at upper right. The hollow impression on the embryo at bottom right might have contained one of the polar bodies. Magnification: x2,000 at 5x7cm size.
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