The Mechanism of Orientation of Freely Moving Littorina Littoralis (L.) to Polarized Light

The mechanism of orientation of Littorina littoralis (L.) to plane polarized light was investigated by means of a servo-mechanism, whereby the intensity of the polarized light was varied with the orientation of the winkle to the plane of vibration. It was shown that these controlled variations in light intensity augmented or decreased the efficiency of orientation. When the light was altered with change in orientation in a direction which would be expected to counteract the Fresnel reflexion/refraction mechanism a fall in responses to polarized light was observed. Random changes in the light intensity of the polarized beam also interfered with the orientation. The influence of reflected patterns of light and shade from the surroundings on the orientation of L. littoralis to polarized light was investigated with the use of the eye shields and with surfaces of different reflective properties. It was conclusively shown that the winkles could orientate both by direct perception of the plane of vibration by the eyes and to comparatively small differences in light intensity in the pattern of light reflected from the substratum.