Fig. 6. (A) CO₂ (black) and water vapour emission (blue) by three batches of eggs from laying to hatching (27°C). Each batch contained 40 eggs. (B) Calculated drop in P_O2 (in kPa) across the wax layer using permeabilities calculated from developmental data in panel A (solid) or and from assuming a constant permeability equivalent that calculated for eggs of age 32 h (see text for details). Because P_O2 at sea level is approximately 21 kPa, this value sets the upper bound on possible P_O2.