LAWS OF CLEAVAGE -
1. Sac's Law - According this law, during cleavage each blastomere to form similar blastomere. New cleavae always take place at the right angle of the first.
2. Pfluger's Law - According this during cleavage mitotic division formation of the spindle fibres proceeds in the region of less resistance.
3. Balfour's Law - According this the rate of cleavage is inversely proportionally to the amount of yolk in the egg.
Rate of cleavage = 1/amount of yolk
4. Hertwig's Law - According this the mitotic apparatus is formed in the centre of the animal pole.