I have numerous silkie eggs developing on day 12 today. I've candled mine quite a few times. I've never seen anything at either END of the eggs. Typically mine are near an outside center area. By day 5 veining was very evident in all developing eggs. If you do not see veining, regardless of what the dark area is, then I do not think it is developing. However, as with several previous posts I did not toss questionable eggs until day 10.