We have 6 runner eggs under our hen. Today is the end of day 10. One egg had definate and immediately obvious veins. The others didn't. They had obvious air cells. Is it possible that they are developing at slightly different rates? Or that the one with the veins has a thinner shell so we could see better. How long should I wait with duck eggs? Thanks, Dana I candled again tonight when it was dark outside. I am using a blindingly bright bike light with a cardboard tube. I only checked out a couple this time as I did not want to disrupt my hen too much. I see dark area's that appear to be yolk, no veins and very well defined air cell. I will not touch them again until the 17th. That's day 10 for the chicken eggs. I didn't find the veiny one again. Too hard in the dark. One problem. One of the eggs has a crack in it. You can't see it with the naked eye in daylight but I saw it when candeling. Should I toss it?