Budgie Egg?

Question
Hey. No eggs and I am about to take out the egg. How can I try breeding again? A few days ago, I shined light on the egg to see and I could only see a type of bubble at one end of the egg. What is this? Also on the other end there are some lines expanding. The lines look like cracks but there are no cracks on it. It's from the inside. If the egg is fertile, how can I hatch it? Please answer ASAP as I think it will be my last question to you.

Answer
I would not try breeding again for a little while, just to give the pair a break.  Take out the nest box, and try again in a few months.  Try giving them some more preparation time next time; giving them cuttlebones, vitamins, and fresh foods so they are in the best health possible.  

The bubble in the egg is exactly what it looks like; and air pocket.  When the time comes for the egg to hatch, the chick is facing that pocket, so if it takes the chick a moment to get out, it can breathe that little  bubble of air.

The egg is probably infertile, considering the parents have been neglecting it.  The air pocket is also an indication of the egg's age.  The larger the pocket, the older the egg.  If it is pretty visible, but there is no chick visible, it is probably a dud.