Discoidal cleavage

Definition
noun
(embryology)A meroblastic cleavage wherein the cytoplasmic divisions are restricted to the animal pole, resulting in the formation of a disc of cells confined at the animal pole or on top of the yolk.
Supplement
This type of cleavage is characteristic of birds, fishes and reptiles in which their eggs contain a large amount of yolk that does not participate in cleavage.
See also: meroblastic cleavage, superficial cleavage