|The egg on the right shows the development of a horizontal blood line near the top, with blood vessels going down from there. Later on the beating heart, and movement will be evident, until the contents are too dense to see much detail.
Eggs are fragile and a flexible flashlight will allow examination without removing from the nest. Check about the 5th day after all have started incubation. The last egg or two may not show development yet, so preserve them. This is a good time also to see if any need repair. When eggs remain for a couple of days after others hatched, check again to determine if any egg stopped developing or they have damage, or the chick died. Do no prematurely dispose of eggs that do not hatch with the others unless you are sure it is dead or stopped developing. The light helps you do this.