It commences with a vertical furrow at the animal pole, extending through about one-fifth of the circumference.
At the animal pole four small cells, entirely formed of protoplasm, are next formed by an equatorial furrow.
The diagrams show the positions of the segmentation spheres and of the contained nuclei as seen from the animal pole.
animal pole n.
The nuclear site in an ovum and the point from which polar bodies are extruded during maturation. Also called germinal pole.