stimulating introduction to a school of thinking and a body of research that is not widely known or easily accessible to us. His attempt to provide a unify ing theory of sensory receptor mechanisms based on evolutionary principles is unique and imaginative. Among the joys of a career in science is the opportunity to rub shoulders with people of outstanding intellectual power and, with luck, to have the privilege of their friendship. In May of 1979 I visited the U.S.S.R. as a guest lecturer in chemical senses. During the 8 days that I spent in the beautiful city of Leningrad I had the great good fortune to become acquainted with Yakov Abramovich Vinnikov, and we quickly became good friends. A dinner party at his apartment is among the warmest of my memories, and nothing could please me more than to have the opportunity to introduce him in per son to my colleagues in Western Europe, the Americas, Japan, and Australia. That, I am sorry to say, is a most unlikely eventuality. For the time being, introducing his fertile mind through this book is the best I can do.