They don't grow in the middle of the egg, the yolk is there taking up room. They're off to one side of the yolk. The white stuff when you crack an egg open to eat it, that's the stuff that holds the yolk suspended inside.
When you candle, if you turn the egg slowly in your hand while holding the light to it, the "blob" should move. As they turn into ducklings, this can also insight a movement from the baby.
Don't worry about end to end, keep the pointy end lower than the fat end. That's all you need to worry about there. Then just keep on turning... x to o, o to x.