Later blastocyst stage , from 17 5 h ( 12 ~ 12 5 h uterine age ) to area pellucida formation after the former egg had been laid .
距前一个蛋产出后175h(12~125h子宫龄)至明区形成期,即鸟类的囊胚期晚期,结果在胚盘中央形成透明的明区和周围不透明的暗区。