Complex sentence: Developing embryos feed on unfertilized eggs within the uterus during the 15 to 18 month gestation period-this is called (oophagy) (i.e. egg-eating).
Split into simpler sentences: Developing embryos feed on unfertilized eggs in uterus during the 15 to 18 month gestation period. This is called (oophagy) (i.e. egg-eating).