General homeostasis of the frequency of circadian oscillations.

Some well-defined statistical regularities characterize the change in period (tau) of cockroach circadian oscillations subjected to a large temperature step. These are explainable in terms of the well-known temperature-compensation (homeostasis) of tau of circadian oscillations. The same regularities are detectable in published data on the effect of several other variables affecting several other circadian oscillations. The proposition is then developed that the temperature-compensation of tau is only a special case of a general homeostatic conservation of the frequency of circadian oscillations in the face of all changes they are likely to encounter in the cell. Such a general homeostasis of tau is a functional prerequisite for an oscillator to function as a useful "clock."