I have been tracking the development of the air cells on my duck eggs by tracing their outlines each time I candle (day 7, day 14, day 21, and just now, at the end of day 24/beginning day 25). 10 of the remaining 12 eggs have had surprising gains in the air cell in just the last three days--equivalent to the amount of gain previously seen after seven days. But in two of them, the gain was almost non-existent. Those same two are different in other ways as well--while the other 10 are almost completely dark except the air cell, these two are only dark in the center two thirds, with the air cell at one end and a light patch at the other. Also, in the lighter section, veins are visible--but they look, to my untrained eye, like they have begun to deteriorate. Are they bad? Should I discard them before lockdown (which is occurring as soon as I stabilize my humidity)? Or give them a chance? They don't smell bad... (yet...). And *is* there a correlation between air cell development and embryo development? I had always thought it was purely a function of evaporation, but I suppose if the peep dies then all its functions cease too and that would probably affect the rate of air exchange....?? I would love input!!