The pole cells form at the posterior tip of the egg in stage 3, when a group of nuclei enters the polar cytoplasm. 3 to 4 nuclei bulge out the membrane of the embryo and form the so-called polar buds. While still connected to the common syncytium the poar buds divide twice. Immediately after the second division the buds pinch off, forming 12-14 pole cells, while the rest of the embryo still resembles a syncytium. During stage 4 most of the pole cells undergo two consecutive mitoses, giving rise to an average of 35 pole cells at the time of blastoderm formation (stage 5).

Pole cell formation, stage 4
Pole cell formation, stage 5