We are now well aware of the influence of sunlight on patterns of activity in animals. These circadian rhythms, roughly matching day and night, are embedded in our genes, and their moleculars mechanisms are now increasingly understood. But what about the light of the Moon? From ancient times, the Moon has exerted a powerful hold on culture. Legends and folklore about the influence of the Moon abound, from werewolves to the best times for fishing. Only recently have scientists begun to look for patterns of behaviour associated with the phases of the Moon. And remarkably, they have found evidence for such circa-lunar biological clocks in a variety of marine and non-marine animals. A number of animals that live close to the shore, such as the flatworm Convoluta and the sea louse Eurydice, which swims in the rising tide and burrows in the sand to avoid being swept into the sea as the tide turns, have internal clocks that have a periodicity matching the Moon-driven tides. Other patterns, such as spawning in some sea urchins, and even spawning in some lake-living fish, far from the reach of tides, have recently been shown to be correlated directly with the intensity of moonlight. Sooty terns, found mainly in tropical regions where there is little variation in day length, appear to have adapted to the stronger environmental cue of moonlight and have a breeding year of ten lunar months. Drawing on such examples, the marine biologist Ernest Naylor gives a fascinating account of the efforts of a small number of scientists, of which he is one, to explore the serious scientific possibility of circa-lunar clocks, and the remarkable evidence they have accumulated. He concludes by looking at the inevitable question: are we humans also susceptible to the influence of the Moon? -- from dust jacket.