Eggs from just laying hens often have blood spots in them though that doesn't sound like what you're seeing. Some people who have never eaten a really fresh egg sometimes wonder about the little spot that, if the egg was fertile, would become the baby chick. It doesn't sould like that's what you're seeing either.
I find that if I look around I can usually find an answer to most of my chicken questions at www.feathersite.com
It can take a bit of clicking and following links but you might find an answer here.