What is this?

[Farmgirlmn]

So I am attempting to incubate some eggs. I wanted to make sure they were fertile and when I cracked this one open there was this thing on the yolk and after two others they had the same thing only smaller. Are they worms? Oh gosh I hope they don't have worms. Help!

 

[gamebirdsonly]

Looks like a blood spot to me. I have a hen or two that always have blood spots on their yokes. Don't know why.