The area‐specific diffusive conductances for oxygen and carbon dioxide of the isolated eggshell compound membrane (CSM), in perpendicular direction (the shortest way between hard shell and chorioallantois), on day 16 of incubation, are 3.38 and 2.00 mmol/(cm2·d·kPa), respectively. Calculated Krogh constants of the CSM for oxygen (K O 2) in lateral (parallel to the shell) and perpendicular (to the shell) directions show marked anisotropy in diffusive properties. The lateral K O 2 is about 100 times the perpendicular K O 2. Analysis shows that eggshell pore density is closely structured to match the diffusive properties of the CSM, ensuring a quasihomogenization of gas pressures in the CSM among adjacent pores. During incubation regional P O 2 (and P CO 2) changes within the CSM may occur as a result of covering relatively small fractions of eggshell. The CSM contributes little to the overall O2 transport resistance in the live egg.