Yes it hatched by itself. It was very quick from pipping hole, zipping, to hatching though. I have it in the incubator in a bowl to keep it away from any others that make hatch. It was the first to hatch.
Chick hatched tonight (very quickly) and has large red sac with visible veins hanging from bottom. It is alternating from walking around cheeping to laying still. I have hatched hundreds of chicks and never seen this. Very concerned. Please advise what needs to be done.