Candling question....rotten egg vs developing egg that quit

[TattooQ27]

Yesterday was day 10 for our duck eggs so we quickly candled our 2 clears to verify that they were still clear and they were. Before tossing them out I opened them up to check what if anything was going on in them. One had a fully intact yolk with a tiny white ring on it, is that considered to be the bullseye that signifies fertility? The second egg yolk looked like someone had vigorously shaken it and it had some light yellow creamy swirl in it with a tiny spot of blood. I am guessing the blood means that the egg at least started but does the liquid yolk with creamy swirl mean it was rotting or is that normal for a developing egg that quit?

 

[BirdBrain]

The first egg was likely fertile but never began to develop. The second was an early quitter and yes that is normal for how the look. When I check clears I break the shell at the level of the aircell by striking it with a knife. Then I pick off the nickel sized peice and look inside. If I can't tell the progress from there I pour it out on a saucer to see what I can. Your swirled egg was not rotten but had great potential for getting there.

 

[TattooQ27]

Quote:
Thank you! I was curious because the 3 shipped eggs I got that went rotten after 12 hours in the incubator looked the same but they were clearly rotten...the smell was very icky.