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Abstract The periodic mating behavior of some stocks of Paramecium aurelia , syngen 3, exhibits features typical of circadian rhythms. In the most extensively studied stock (37 p ), rhythmicity persists at least four days in continuous darkness, but disappears rapidly in continuous illumination (200 foot‐candles). The period of the free‐running rhythm is 22.2 hours, and relatively insensitive to ambient temperature. Cycles of illumination and temperature can regulate the mating rhythm. Changes in illumination at specified times in the circadian cycle will induce shifts in the phase of the rhythm. Stock differences with respect to the persistence of the rhythm and the environmental control of its phase have been observed.
Marlene W. Karakashian (1968) studied this question.