Coelom. It is partitioned by septa, which is a divider between segments of the worm.
they have a coelom
Roundworms are pseudocoelomates
Annelida
Yes, they do. They have true coeloms, i.e. their coeloms (body cavities) are lined with mesodermal (referring to the embryonic germ layer which forms the muscles, nervous system, and generally the...