In 1929, a group of scientists, working at Oxford University, began "the pursuit of the ecological Holy Grail," an endeavor devoted to the search for the secret mechanisms behind biological life cycles as they occur in many animal populations. By 1935, the group had become the Bureau of Animal Population and was joined for one year, part-time, by a newly minted graduate of the University of Toronto. Twenty-six years later, when he returned to Canada. Dennis Chitty had learned much about cycles and even more about the process of science. The results are presented here in an intriguing and often irreverent account of science, not as it should be, but as it was and is. Unlike many science books which tell of successful ventures and satisfactory conclusions, this book reveals the harsher but more common story of a scientific question left unanswered. Written by one of this century's most distinguished small-mammal ecologists, it is both a personal history and a vigorous defense of a life in pure science - even when no final dramatic closure was reached. Included along the way are important accounts of the pioneering work of Charles Elton, from which much of modern population biology has grown, and insights on the philosophy and practice of science.