This book is a study of the embryology of animals—the development of embryos from the egg to hatching or birth. It provides an overview of the historical and theoretical underpinnings of embryological thought, offering a thematic examination of some of the most fundamental questions that have engaged scholars in this field. What are the factors that trigger the development of an embryo? How do genes influence the growth and differentiation of tissues? What are the mechanisms that ensure that the myriad cells in an organism are organized into a coherent and functional whole? These are just a few of the fascinating topics covered over the course of the book. Grounded in the historical development of the field and incorporating detailed descriptions of embryological phenomena, the author traces the evolution of embryological thought from the speculative philosophies of Aristotle to the era of molecular and genetic research. The result is a comprehensive introduction to the history, theory, and practice of embryology that will appeal to scholars and students alike.