PRIMITIVE NERVOUS SYSTEMS. A SENSORY NERVE-NET IN THE POLYCLAD FLATWORM NOTOPLANA ACTICOLA

¹ Developmental and Cell Biology, University of California, Irvine, Irvine, California 92664

(1). The response to mechanical stimuli in the polyclad flatworm, Notoplana acticola, is the initiation of ditaxic locomotion. The response to electrical stimuli is local contraction.

(2). Animals will respond to mechanical stimuli with ditaxic movements even if a series of cuts are made so that the stimulus must be propagated around lesions as in a nerve-net.

(3). Only the sensory side of the system is organized as a diffusely conducted system; motor control involves direct connections to the brain.

(4). Sensory stimuli that convey information about the location of a stimulus on the body also require direct routes.