Epibolyis the process of [CBSE PMT 1992]

• A. Mass migration of cells from theanimal hemisphere so that upper micromeres begin to migrate over theedge of the dorsal lip and roll inside and are tucked beneath the outer layer
• B. Over growth when the micromeres divide rapidly and begin to spread downwards over the megameres except at the yolk plug
• C. Rotation of gastrula within the vitelline membrane so that the animal pole becomes anterior
• D. Formation of a small slit like invagination occuring on the gray crescent