Abstract
Circadian rhythms are known with many organisms from single-celled flagellates to higher plants and animals. However, a relatively small number of circadian rhythms have been investigated in enough detail. The characteristics of the circadian rhythms were mentioned mainly aobut the rhythms of the common bean, Phaseolus, and of Gonyaulax. The most striking thing about the circadian rhythms is their uniformity between different organisms and temperature independence of the period length. Although the models were constructed by a number of investigators, the mechanism of the time-measuring system of the rhythm is unknown at now.
It was discussed lastly about Bunning's proposal that the same timing mechanism as the circadian rhythms is responsible for photoperiodic timing.
