EPIBOLY -

1. The epibolic movements occur only in the prospective ectodermal blastomeres.
2. In the blastula of frog, migration and rearrangement of microceres over megameres is called epiboly.
3. At one specific point micromeres do not cover megameres, this place is known as gastrulation slit.
4. This slit is blastopore of future embryo. Formation of blastopores occurs in grey-crescent area.
5. Some megameres start budding as result of this budding micromeres are formed.
6. These micreomeres also cover the megameres. This process is known as Apiauxesic.
7. Example - In the eggs of Ctenophora, Mollusca, Annelida