DURATION OF AN AFTER-EFFECT IN PLANARIANS FOLLOWING A REVERSED HORIZONTAL MAGNETIC VECTOR

Abstract

Dugesia dorotocephala creeping geographic northward in an unvarying pattern of illumination turn more strongly clockwise in response to a reversed 4-gauss than to a 0.05-gauss vector. After termination of a 15-min. exposure to a 0.05-gauss vector the worms turn more strongly counterclockwise, and after a 4-gauss one more strongly clockwise, than control worms before such exposures. This modified behavior is gradually lost, exponentially, over the course of 20 to 25 min. When left continuously for 40 min. in reversed vectors there appears to be a slight, but transient, accommodation to the experimentally altered fields during the first 20 min, but this partial accommodation appears to be lost completely before the end of 40 min. Evidence is presented which suggests that other uncontrolled ambient geophysical fluctuations modify response to the reversed magnetic vector.