eighteen of the polyspermic zygotes ( 14 with three pronuclei and 4 with four pronuclei ) were obtained from zona pellucida-intact oocytes , and seven ( 1 five-pronucleate 3 four-pronucleate , and 3 three-pronucleate ) from previously zona-drilled oocytes .
C0043519
zona pellucida
C0029045
oocytes