A description of Chlamydodon, probably a variation of the species mnemosyne, found in brackish water at Woods Hole, is presented. There is a complex neuromotor apparatus, including a coördinating center, and systems of fibers connected with cilia, the mouth opening, the phryngeal basket, and the "railroad track." The connection of the fibers with the organelles and the central mass, or motorium, the behavior of the animal after the destruction of the motorium, seem to suggest a coördinating function for the system.