Opaque Sac inside egg - What is it?

[Anime2lover]

I love finding things like this! I have never had an egg inside of an egg like this, but a very aged bantam hen once laid me an egg inside of another shell.

Isnt that pretty much the same??

 

[aart]

Could have absorbed the premie yolk before it got the shell.

Probably immature yolk got released with mature one and the were just enveloped in same shell...like a double yolker.

Isnt that pretty much the same??

Shelled egg inside shelled egg is when reverse-peristalsis happens,
a fully shelled egg backs up in the tract and gets enveloped with the next egg coming down the tract.