This volume is the twenty-ninth in this series, which includes twenty-eight numbered volumes and one unnumbered supplement. The editors continue to focus on critical reviews, commentaries, original papers, and controversies in of the reviews range from anthropology to evolutionary biology. The topics molecular evolution, population biology to paleobiology. Recent volumes have included a broad spectrum of chapters on such subjects as population biology, comparative morphology, paleobiology, molecular phy logenetics, developmental evolutionary biology, systematics, and the history of evolutionary biology. The editors continue to solicit manuscripts in all areas of evolutionary biology. Manuscripts should be sent to anyone of the following: Max K. Hecht, Department of Biology, Queens College of the City University of New York, Flushing, New York 11367; Ross 1. MacIntyre, Department of Genetics and Development, Cornell University, Ithaca, New York 14853; or Michael T. Clegg, Department of Botany and Plant Sciences, University of California, Riverside, California 92521. vii Contents 1. Homology and Embryonic Development Brian K. Hall Introduction. 1 A Brief History of the Concept of Homology. 1 von Baer's Laws. 4 Germ Layers and Ernst Haeckel. 6 Embryology and Homology. 7 Homology: An Unsolved Problem. 8 Latent Homology. 8 Serial Homology. 9 Common Origins and Common Inductions. 12 Mechanisms of Gastrulation. 13 Origin of the Alimentary Canal. 14 Origin of Germ Cells. 14. Induction of Meckel's Cartilage. 15 Induction of the Lens of the Eye. 16 Development of Internal and External Cheek Pouches. 18 Selection for Increased Tail Length in Mice. 19 Regeneration and Homology. 20.