In Cells, Embryos and Evolution the authors' ambition is to continue what Charles Darwin began: to understand not only the influence of selection on evolution but also the capacity of an organism to generate heritable variation upon which selection can act. Drawing on the theories derived from molecular, cellular and developmental biology in the past 20 years, John Gerhart and Marc Kirschner have begun to explain the origins of phenotypic variation and evolutionary adaptation from within eukaryotic cell biological and developmental processes. This has required them to confront the following paradox: on the one hand, deep cellular and molecular conservation and the extraordinary stability of body plans of the major metazoan phyla; and on the other hand, the rapid diversification of the anatomy and physiology of organisms. Cells, Embryos and Evolution is richly illustrated with examples drawn from modern palaeontology, developmental biology, and cell biology. It sets out to establish a coherent basis for evaluating the role of cellular and embryological mechanisms in evolutionary change.