one vein around whole egg. what is this?

[TheBeardie]

I have one of my eggs that has a ring around the egg. One vein around the whole egg. The egg has a round dot above the vein that moves. That would be the chick(?) It looks way behind on development compared to the other eggs that are also on day 15. What is this?

 

[Pyxis]

It's a blood ring. The embryo started developing and then died. Sorry