A cracked egg CAN hatch if the membrane has not been torn. I had a turkey egg that had a huge dimpled crack the side of a dime as well as trailing crack lines that spread out to about the size of a nickle (tractor ran over the nest). Anyway, since the egg wasn't leaking I took that to mean there was a chance the membrane was still intact and so I sealed the dimpled crack and all of the crack lines with a bit of melted wax from a left-over birthday candle. The egg not only made it through almost three weeks of incubation under a first time broody hen, but also hatched out a perfectly healthy and active turkey poult.