Colonial nervous control of lophophore retraction in cheilostome Bryozoa.

Nervous impulses causing lophophore retraction over large areas of Membranipora membranacea and Electra pilosa were recorded with external electrodes. The response propagates at about 100 centimeters per second, presumably through the colonial nerve plexus of Hiller and Lutaud. Impulses are rapid up to 200 per second. A second impulse was recorded from individual zooids, probably generated by the polypide's nervous system. The retractor muscle shortens at more than 20 times its own length per second and is apparently the most rapidly contracting muscle known.