ANATOMY

Detailed explanation-1: -They are as follows. (1) Meridional plane : When cleavage furrow bisects both the poles of the egg, passing through the animal vegetal axis, the plane of cleavage is called meridional plane.

Detailed explanation-2: -When a furrow bisect both the poles of the egg passing through the median axis or centre of egg it is called meridional plane of cleavage. The median axis runs between the centre of animal pole and vegetal pole.

Detailed explanation-3: -1. Meridional plane: The plane of cleavage lies on the animal vegetal axis. It bisects both the poles of the egg. Thus the egg is divided into two equal halves.

Detailed explanation-4: -Especially, the first cleavage plane is through the animal–vegetal axis in many animal species including the starfish and sea urchin, and divides the egg in equal blastomeres. The cleavage furrow forms equidistantly between the two poles of the mitotic apparatus (MA) (Hiramoto, 1956, Rappaport, 1971).

Detailed explanation-5: -cleavage, in embryology, the first few cellular divisions of a zygote (fertilized egg). Initially, the zygote splits along a longitudinal plane. The second division is also longitudinal, but at 90 degrees to the plane of the first. The third division is perpendicular to the first two and is equatorial in position.