The last ten years have shown a dramatic revolution in our understanding of early animal development. This new edition of the successful first edition describes the result of this revolution and explains how the body plan of an embryo emerges from the newly fertilised egg. The book starts with a critical discussion of embryological concepts and explains in simple terms the mathematics of cell states, morphogen gradients and threshold responses. The experimental evidence on the mechanism of regional specification in Xenopus, molluscs, annelids, ascidians as well as Caenorhabditis, the mouse, the chick and Drosophila is then discussed. The whole chapter devoted to the exciting developments in Drosophila provides a clear guide to the subject, including a new table outlining the developmentally important genes. The emphasis throughout is on conceptual clarity and unity: bringing together the mathematical models, embryological experiments and molecular biology into a single, comprehensive coherent account.

"One of the best and clearest explications of the bewildering terminology of embryology that I have ever come across...It would be difficult to find another book where the central facts of early embryonic development are set forth so clearly and economically...Slack establishes himself as an excellent expositor and critic of biomathematical theory." Cell

"The tone of the discussion is non-partisan as between competing theories, but thoughtful and often provocative. Many questions are posed for the reader to ponder, where other authors might peddle their own pet speculations...it is entertainingly written; it gives a clear and refreshing perspective on a major problem; and, above all, it stimulates thought." Nature

"...a singular and critical exploration of a central development problem, uncluttered by superfluous detail and, apart from the occasional bias, rigorous in evaluation of the evidence. The unpatronizing, bossy style draws the reader into the problem and it is one of those unusual science books that one can actually read rather han refer to." Rosa Beddington, Trends in Genetics