ABSTRACT
A study of the anemone Calliactis parasitica (Pantin, 1935) showed that its most obvious activities are of a peculiarly simple kind. The unstimulated animal seems to be inactive. Activity originates directly as a response to external stimuli. Thus an adverse mechanical stimulus to the passive animal sets up impulses, transmitted by a special ‘through-conduction system’ which in this species activates the marginal sphincter muscle of the oral disk. The closure of this muscle protects the disk. Again, when food touches the tentacles, it is conveyed to the mouth by a series of local responses. In both these instances the activity consists of responses directly related to external stimuli, and the animal behaves as a passive vehicle for the conduction of excitation.
