Egg within an Egg

Harry was proud to show me his discovery: an egg within an egg. We’ve read about this before, and for years whenever we’ve found an especially large egg the kids have eagerly gathered round the skillet to see if we had a nested egg. This is the first one we’ve found.

This egg didn’t have a fully calcified coating on the second membrane so the outer layer broke on handling.  But it did have a separate yolk and albumen along with the inner egg. The inner egg turned out to be a relatively normal double-yolk egg.  Alas, no infinite egg recursion…

Double Yolk

Just a (relatively) normal double yolk egg on the inside.

The phenomena occurs when an egg moves backwards through a hen’s oviduct, causing the next egg being released to encompass the previous one.  In a typical situation hens release a yolk from the ovary, then it moves through stages of the oviduct, first being fertilized (if sperm is present), then it goes through a long passage where the albumen (the white of an egg) and the membranes are built, then it moves to a gland where the shell is formed.  After that, the egg normally is conveyed outward by peristalsis to be laid, but under rare circumstances the egg might move back upstream, encounter the next egg coming down, and become enclosed as a double egg.  The fact that the inner egg in this case was a double-yolker points to the likelihood that the large size caused a temporary blockage and led to this occurrence.

3 Comments on “Egg within an Egg

  1. I have encountered this just once on a supermarket-bought egg. I wonder what would happen if the egg was fertilised and allowed to hatch?

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