What is this?? ( Duck eggs )

[Draga Devia]

Hello. I candled my duck eggs today (day 7) and i removed the one that had no veins or anything at all inside..
As I opened 1 egg there was this strange white thing attached to the yolk (the egg smelled a bit bad) but there was no veins and it did not look fertile at all... Do you know what it could be?



Thanks
Draga

 

[cmfarm]

It looks like maybe it started to develop and quit maybe?