What was this?

[rwreef]

This is a picture of a coral I had a while back and has since died back completely. I was wondering if anyone may know what the white things were on this coral?

 

[tsouth]

"Mesenterial filaments are string-like extensions of the mesenteries—the internal folds of tissue which create structure within a coral polyp's body. They are typically bright white and full of nematocysts—specialized stinging cells that corals use to capture and kill prey, and to sting their competitors"