Effects and After-effects on Planarians of Reversals of the Horizontal Magnetic Vector

THE freshwater planarian, Dugesia dorotocephala, was investigated at Evanston, Illinois, to learn whether it, displayed orientational responses to abrupt experimental reversals of the horizontal vector of magnetism comparable with responses recently reported for marine mud-snails, Nassarius obsoletus, at Woods Hole, Massachusetts1. The study of the planarians extended over the period from April 12 to September 25, 1962, which included nearly 6 synodic months.