LadyHawkeAvry
Songster
I did that with the third egg/chick. After she pooped all over the one that's still brooding...I didn't want to take a chance with this egg, so I put it in my incubator. When it started to zip, I slipped it under her to finish hatching.
This last egg...I've never seen it where there was absolutely NO visible space inside the egg! No air cell to see, no chick outline...nothing. It's solid black all the way around. I'll do the float test and see if there's any movement.
In my experience, the eggs that go all dark are eggs that pipped internally but not externally. Instead of rotating to begin unzipping, they rotate back inwards, leaving a back or rump in the air cell. I went back through my records - had the same thing on egg #85 - a pheasant egg, last of the clutch. The egg went dark - eggtopsy showed internal pip without external pip and rotation of the chick. (Yeah, I'm one of those über nerds who keeps insanely detailed records of my incubation and hatches...)