I am a newbie hatcher. After having two small batches of duck eggs not develope (bad air cells and some frozen) I got 8 chicken eggs in the mail and some are developing by day 4! So don't give up! It's hard to get good quality chicks where I live, so by mail is a good way to try. Out of 8 eggs, 4 have dislodged air cells and look clear. I will wait a few more days and toss. But the best thing is I see spider veins in a couple! Now I know what everyone is talking about!!! And a heart beating is amazing already at day 4. A couple developing have funky air cells so I hope they make it to the end. BYC has helped me not give up....shipped eggs are hard. Thanks everyone on here for your wonderfully helpful posts!