Energid

The fate of the cleavage energids seems to be determined by the regional nature of the periplasm, because elimination of some of the migrating energids by ultraviolet irradiation produces no structural deficits in the embryo; other energids replace them (Seidel, 1932).

Nuclei and associated cytoplasm are referred to as energids. Upon reaching a critical density, the energids migrate to the periphery of the egg. The arrival of the energids at the surface is sometimes visually apparent as bumps along the surface. At the periphery, the energids continue to undergo several rounds of division.

Rather, the embryo develops in a plasmodial state, containing eventually hundreds of energids, i.e. nuclei with jackets of cytoplasm. Some energids remain as vitellophages in the endoplasm, while most energids enter the yolk-free periplasm at the surface.