ABSTRACT
It occurred to the author that it was possible that some relation might be found to exist between the reactions of animals to stimuli and their physiological polarity and symmetry relations. It was necessary to use as stimulus some form of energy that was both continuous in action and controlled in direction. Light, though much used in experiments on animal reactions, would here prove unsuitable because of the variable nature of the responses called forth, and because a number of conditions alter the sign of phototropic response. Electrical current was chosen, and, since Planarians are animals in which physiological polarity is known to exist, and on which much work has been done, Polycelis nigra was used as the subject of experiment.
In all experiments in this paper where movement occurred parallel to the electrodes in the current it appeared to be physically easier than in the direction of the current, and ciliary action took place more frequently under these conditions. It almost seems as if these animals had temporarily thrown off the orientating effects of the current “with relief,” and had exchanged the electrically induced looping for the normal ciliary gliding action.
Protozoa (Loeb), Planaria (Pearl), Polycelis and Daphnia (Robertson) are kathodic. Verte-brates, Crustacea (Loeb) and Corixa (Robertson) are anodic in reaction.
