Vestimentum
Though it may not look like much, this part of the worm is like Mission
Control. A muscular structure, it helps to anchor the upper portion of the worm
in the tube. It provides safe passage for the blood heading from the plume to
the trophosome. It generates new tube material. It holds the
reproductive pores from which the worm releases sperm or eggs during spawning;
these combine in the water to make baby tubeworms. Finally, along with various
glands, this structure harbors simplified versions of the two organs that most
closely bind this primitive creature to its fellow animals: the heart and the
brain.