The Crinoid Stem Lumen
The stem of the stemmed crinoids is constructed of a
series of inter-locking disks called "columnals",each of these columnals
are centrally perforated creating a lumen down the center of the stem.
This lumen houses the canals and nerves of the coelomic chambered
and axial organs
which, among other things, are involved in the movements of the animal.