Abstract
Conclusions
1. The flicker fusion frequency-intensity relations differ for the light-adapted day and night-phase eyes. 2. This difference is marked in the high intensity range and decreases as the threshold intensities are approached. 3. In view of data published elsewhere the reversal of sensitivity relationships indicates that the process of light-adaptation is much more pronounced in the nightphase than in the day-phase eye. 4. The flicker response contour and other relationships confirm the conclusion, made elsewhere, that the diurnal rhythm present in the eyes of these beetles results in two physiological states which are so different that they may be considered functionally as separate and distinct photoreceptors.
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