Principles Governing Cleavage
a) The nucleus and mitotic achromatic figure tend to occupy the centre of active cytoplasmic density of the dividing cells, e.g., in isolecithal eggs or microlecithal eggs, the spindle is formed centrally in the cell while in the telolecithal eggs, and it is formed nearer the animal pole.
b) Each new cleavage furrow tends to intersect the plane of the preceding cleavage furrow at right angle.
c) The cells or blastomeres tend to divide into two equal sized daughter cells unless yolk is unevenly distributed.
d) Free sides of the blastomeres tend to become rounded.