The amount of yolk and how it is distributed determines the type of cleavage. On this basis cleavage is of two types: (a) Holoblastic - where the segmentation line passes through the entire egg. It occurs in alecithal (without yolk), microlecithal (with very little amount of yolk) and mesolecithal (little amount of yolk) egg. (b) Meroblastic - where segmentation line does not pass through the egg and remained confined to a part of the egg. It occurs in megalecithal (large amount of yolk) egg.