RESPONSE OF THE PLANARIAN, DUGESIA, TO VERY WEAK HORIZONTAL ELECTROSTATIC FIELDS

¹ Department of Biological Sciences, Northwestern University, Evanston, Illinois

1. The planarian Dugesia is able, even while in water, to perceive a change of 2 volts/cm. in electrostatic gradient in the surrounding air.

2. There is reason to presume that in order to show this response the organism is responding to differences in ambient static gradient of the order of fractions of a microvolt per cm.

3. The strength and character of worm response to a right-angle potential change are related to the direction the worm is oriented in the earth's geographic field, and to time of day.

4. A field-change in South-bound worms in the morning effects clockwise turning. A similar field-change for North-bound worms effects counterclockwise turning. In the afternoon the relationship of electrostatic response to geographic direction is essentially the mirror-image of that of the morning.

5. Dugesia is able to distinguish the direction of a gradient across its body.

6. A few of the possible significances of these findings are discussed briefly.