The cloaca is divided by transverse circular folds, which project from its inner walls, into three successive chambers.
Trophi virgate exsertile; germary paired; genito-urinary cloaca opening above the neck in the male, subapically in the female.
Gut blind (Paraseison), or opening into cloaca (Seison).
The mouth is terminal or subterminal; there is a weak sucking pharynx situated behind the brain, and a long intestine lying along the medio-ventral body-cavity; it ends in a cloaca which receives the vasa deferentia in the male.
The Nematomorpha form an isolated group; at first sight they seem to be connected with the Nematoda, but in reality their only common feature is the tubular genitalia opening into a cloaca, and it seems at present impossible to connect them with the Annelida.