Retinal Orientation and the Discrimination of Polarized Light by Octopuses

Abstract

1. The object of the investigation was to show that the ability of Octopus to detect the plane of polarization of light does not depend upon differential reflexion from its surroundings. 2. Animals were trained to distinguish between light plane polarized in the vertical plane (normal to the iris slit of the intact animal) and in the horizontal plane (parallel to the slit). 3. The statocysts were then removed, abolishing the normally fixed orientation of the eyes with respect to gravity. 4. After the operation the plane of polarization was set at each trial so as to be either normal or parallel to the iris slit. Because the eyes were now disoriented, there was no longer any constant relation between these planes and the fixed reflecting surfaces of the aquarium. 5. The animals, nevertheless, continued to discriminate correctly. It is therefore concluded that detection of the plane of polarization depends upon some intra-ocular mechanism.