Question

Epiboly is the process of

• A. Mass migration of cells from the animal hemisphere, so that upper micromeres begin to migrate over the edge of the dorsal lip and roll inside and are tucked beneath the outer layer.
• B. Over growth, when the micromeres divides 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 occurring on the grey crescent.

Answer 1

Answer: (B)

Over growth, when the micromeres divides rapidly and begin to spread downwards over the megameres except at the yolk plug.

Gastrulation is accomplished by epiboly, wherein the micromeres at the animal pole multiply and overgrow the vegetal macromeres. Eventually, the micromeres will cover the entire embryo, leaving a small slit at the vegetal pole.
Thus, the correct answer is option B.