How do I know my eggs are fertile or not?

[Carrie]

My Russian recently had two eggs approximately 10 days ago. I have had them in an incubator since the first day she had them. When I candle them from the top I don't see anything inside and it seems clear all the way through. This is her second clutch. She had only one egg in her first clutch and it was not fertile. How long do you think I will have to wait to see if they are fertile?

 

[TortoiseRN]

http://russiantortoise.net/index.htm

This is a pretty good site. It has some great pics of developing eggs and time line.