the preovulatory oocytes , before they were used for in vitro fertilization , consisted of : 1 ) those cultured in vitro for 4 to 6 h to permit final maturation and 2 ) those incubated in the rabbit oviduct for 4 to 5 h to permit final maturation and induce hardening of the zona pellucida .
C0029045
oocytes
C0043519
zona pellucida