The Evolution of Differentiation attempts to sketch the outlines of a framework from what is now known or suspected of the various aspects of differentiation in all types of organisms. This book surveys the many aspects of differentiation that are seen today, and in particular, because of the evident universality of expression of the genetic code, to enquire whether any similar universality exists in the methods of gene repression and activation. The information reviewed ranges from the chemical control of the genetic mechanisms of unicellular organisms during their various phases of activity, to the chemical control of differentiation in multicellular organisms both during embryonic development and in the adult state. Finally, some consideration is also given to that collapse of differentiation which leads to cancer.