protovum

from The Century Dictionary.

• noun An original or primitive egg; an ovum or ovule in its first state, as when still in its Graafian follicle, or, in general, before its impregnation, when it becomes a cytula or parent-cell by fecundation with sperm; or, in the case of meroblastic eggs, an undifferentiated female egg-cell before it acquires the mass of nonformative food-yolk which converts it into a metovum.