Thought you'd like to see this since so many have asked how to tell if their eggs are fertilized. The first picture is an INfertile egg.
On this one, you can see the ring, indicating fertility. This is caused by cells in the center of the blastoderm dying off and leaving a cleared out area, making that bullseye appearance. Not all are as clear as this one is, but you get the idea.
**sorry for the graininess of these photos, but they were from years ago and a not so great camera.