Ah! Well, if you have no more due to hatch right now, then you could candle to check them. In ones that are growing you should see a nice network of veins showing. However, they do get darker as the chick grows to fill more of the shell. But you should still be able to see veins at the edges of the air cell if your light is bright enough. Here is a link to a thread that has some great info and candling progression pics so you know what to look for.

