The acrosome reaction, exposes the inner acrosomal membrane to the outside. The junction between this inner acrosomal membrane and the sperm cell membrane is called the equatorial region, and this is where membrane fusion between sperm and egg begins

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P2 cell establishes the

dorsal-ventral axis of C. elegans and confers on the ABp blastomere a fate different from that of its sister cell.

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In embryos whose mothers have mutant glp-1, ABp is transformed into an ABa cell

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If the P2 cell is killed at the early 4-cell stage, the ABp cell does not generate its normal complement of cells

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Cleavage type- Unequal radial holoblastic cleavage

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Cortical Rotation The cortical cytoplasm has rotated 30º relative to the internal cytoplasm.

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Gray Crescent 

The region opposite the point of sperm entry, where the greatest displacement of cytoplasm occurs (Gastrulation will begin)

Vegetal rotation: Vegetal cells asymmetrically press up against the inner blastocoel roof on the dorsal side.

Bottle cell formation and invagination: Localized apical constriction at the dorsal blastopore lip creates anisotropic forces that foster invagination.

Involution and cell migration: The leading edge of invaginating cells crawls up onto the blastocoel roof.

Convergence and extension: The targeted medial-to-lateral intercalation of cells on the midline (convergence) drives anterior-posterior axis elongation (extension).