This is not a good sign. It is actually a pus packet referred to as a "lash egg."
It means there is serious inflammation inside the ova duct. The overall prognosis is not good for most hens.
You can read more about it here:
Sorry. Hopefully with a good round of antibiotics the hen can be helped, but often scarring is permanent and culling may be a kindness as the hen is ripe for egg binding or more internal infection.
Look at the hen that has not been laying as she is most likely to have laid the lash egg. She probably has had an infection for weeks which is the reason she has not been laying.
Edited by Lady of McCamley - 4/14/16 at 8:52pm