* Water lost from the egg is replaced by air, creating the 'air cell' at the blunt end of the egg.
* Water lost from the egg is replaced by air, creating the 'air cell' at the blunt end of the egg.
−
* Embryo punctures the chrioallantoic and internal shell membrane.
+
* Embryo punctures the [[Exotics_-_Composition_of_the_Egg_-_Anatomy_%26_Physiology#Embryonic_Membranes|chorioallantoic]] and internal shell membrane.
** Able to begin pulmonary ventilation, rebreathing the 'air cell' gas.
** Able to begin pulmonary ventilation, rebreathing the 'air cell' gas.
−
** Transition from diffusive respiration through the chorioallantois to breathing through the lungs.
+
** Transition from diffusive respiration through the [[Exotics_-_Composition_of_the_Egg_-_Anatomy_%26_Physiology#Embryonic_Membranes|chorioallantois]] to breathing through the lungs.