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.