Ruh roh, what happened here? (egg pic)

[jessellebond]

Obviously he's a goner, any ideas what happened? All my other guys are going strong, and this one had started developing and the kaput.

Here's another of my eggs (for comparison of the same batch) that is doing fabulous:

 

[Amiga]

I am not a hatcher, but I have been reading some of the posts from them.

It seems that for unexplained reasons, some just hit a point in development where something goes wrong. This apparently can happen at most any stage. Mother ducks may kick some eggs out of the nest, and the supposition is that somehow she can tell if there is a problem.