Hi everyone! I'm wondering if no visible air sac means no fetus? I have an incubator with 12 various chicken eggs going, and I've marked the 7-day air cells (per the wonderful advice found here at BYC), but I have one egg that I can't make out an air cell. (is it air cell or air sac???) I can see a darker mass that floats around when i handle the egg, but I can't make out any edges to the mass, no veins, no eyeball like the other lighter shelled eggs I've got going in there. Any opinions? I'll wait til day 10 at least, before I do anything drastic, just wanted to get some thoughts. Thanks!