I have been incubating eggs for years and have never found anything like this before and am wondering if anyone else has? The chick was supposed to hatch yesterday. It was a brown egg--either from a Black Sex link, Comet, or Barred Rock hen and the rooster (only one I have) was an Ameracauna. Since all other eggs hatched a day earlier than they were supposed to I decided that this one was probably dead and I was going to open it up to see what had happened to it. I was incubating 42 eggs and had 35 healthy chicks hatch. What a surprise to see that although it was dead, it had 4 legs, 3 wings, 2 backs and 2 cloacas, one visible head but I think judging by the size of the neck it might have had extra tissue there. It looks like it had a blister on the top of its head too. Its abdomen was wide open and the yolk was rather large and still attached. I have pictures but they are kind of graphic and I don't want to offend anyone.
I wonder how this happened? There was only one yolk in there!