ABSTRACT
Phenomena that seem mysterious, such as dreams and biological rhythms, attract both awe and superstition. The idea of a biological cyclicity in the dream process, because it combines two exotic areas of scientific learning, may seem doubly magical. Yet a growing body of confirmatory investigations from numerous laboratories now allows us confidence that there are real cyclic processes related to dreaming. Still more fanciful might seem hypotheses that a cycle of dreaming, or something like it, occurs in the waking person. It is with such hypotheses that this presentation is concerned. Starting with a historical perspective, we may see that some such hypotheses were indeed rather imaginative, but we shall also find that modified hypotheses are attracting an increasing body of experimental support.
