STUDIES IN THE PIGMENTARY SYSTEM OF CRUSTACEA

III. LIGHT-INTENSITY AND THE POSITION OF THE DISTAL RETINAL PIGMENT IN LEANDER ADSPERSUS

¹ From the Biological Laboratories, Harvard University, and the Department of Zoology, Oxford University

1. On a constant background the amount of migration of the distal retinal pigment in Leander adspersus is directly proportional to the intensity of incident light, within the limits of light- and of dark-adaptation.

2. Under the conditions of illumination used in these experiments the position of the distal retinal pigment is in direct proportion to the ratio, intensity of incident light/intensity of reflected light.

3. In alleyes, except those completely light- and totally dark-adapted, the pigment is found to migrate to a greater extent in the dorsal half of the retina. The reason for this variation in position of the pigment of the dorsal and ventral portions of the retina is not clear.