The vertebrate eye has been, and continues to be, an object of interest and of inquiry for biologists, physicists, chemists, psychologists, and others. Quite apart from its important role in the development of ophthalmology and related medical disciplines, the vertebrate eye is an exemplar of the ingenuity of living systems in adapting to the diverse and changing environments in which vertebrates have evolved. The wonder is not so much that the visual system, like other body systems, has been able to adapt in this way, but rather that these adaptations have taken such a variety of forms. In a previous volume in this series (VII/I) Eakin expressed admiration for the diversity of invertebrate photoreceptors. A comparable situation exists for the vertebrate eye as a whole and one object of this volume is to present to the reader the nature of this diversity. One result of this diversification of ocular structures and properties is that the experimental biologist has available a number of systems for study that are unique or especially favorable for the investigation of particular questions in visual science or neurobiology. This volume includes some examples of progress made by the use of such specially selected vertebrate systems. It is our hope that this comparative approach will continue to reveal new and useful preparations for the examination of important questions.

A question often asked of those of us who work in the seemingly esoteric field of fish vision is, why? To some of us the answer seems obvious - how many other visual scientists get to dive in a tropical lagoon in the name of science and then are able to eat their subjects for dinner? However, there are better, or at least scientifically more acceptable, reasons for working on the visual system of fish. First, in terms of numbers, fish are by far the most important of all vertebrate classes, probably accounting for over half (c. 22 000 species) of all recognized vertebrate species (Nelson, 1984). Furthermore, many of these are of commercial importance. Secondly, if one of the research aims is to understand the human visual system, animals such as fish can tell us a great deal, since in many ways their visual systems, and specifically their eyes, are similar to our own. This is fortunate, since there are several techniques, such as intracellular retinal recording, which are vital to our understanding of the visual process, that cannot be performed routinely on primates. The cold blooded fish, on the other hand, is an ideal subject for such studies and much of what we know about, for example, the fundamentals of information processing in the retina is based on work carried out on fish (e. g. Svaetichin, 1953).

1 Kevin Moses It is now 25 years since the study of the development of the compound eye in Drosophila really began with a classic paper (Ready et al. 1976). In 1864, August Weismann published a monograph on the development of Diptera and included some beautiful drawings of the developing imaginal discs (Weismann 1864). One of these is the first description of the third instar eye disc in which Weismann drew a vertical line separating a posterior domain that included a regular pattern of clustered cells from an anterior domain without such a pattern. Weismann suggested that these clusters were the precursors of the adult ommatidia and that the line marks the anterior edge of the eye. In his first suggestion he was absolutely correct - in his second he was wrong. The vertical line shown was not the anterior edge of the eye, but the anterior edge of a moving wave of patterning and cell type specification that 112 years later (1976) Ready, Hansen and Benzer would name the "morphogenetic furrow". While it is too late to hear from August Weismann, it is a particular pleasure to be able to include a chapter in this Volume from the first author of that 1976 paper: Don Ready! These past 25 years have seen an astonishing explosion in the study of the fly eye (see Fig.

This book presents an overview of the entire field of cadherin research and provides the current basic concept of cadherins. Cadherins have been widely accepted as key regulators of animal development and physiological functions, and it also has become clear that they play essential roles in various human diseases. With contributions by leading scientists, the book covers various aspects of the cadherin superfamily including the history of cadherin research, basic properties of classical cadherins as well as non-classical cadherins, cadherin-associated proteins, and the roles of cadherins in health and diseases. In addition, the book presents some contradictory results and important unanswered questions, and the authors propose their working hypotheses or future directions, to inspire future studies. This volume enables graduate students and young researchers to learn the basics and gain a comprehensive image of the cadherin superfamily, and experts in the field will easily find various topics of interest in relevant areas of study. Additionally, a list of cadherin-related diseases is included for quick reference to cadherins in human diseases.

Development of the Visual System presents a selection of current studies that clearly illustrate principles of visual system development. These range from retinal development in fish and frogs to the effects of abnormal visual experience on the primary visual cortex of the cat. The book is unique in addressing four specific and fundamental aspects of development: cell lineage and cell fate, specificity and targeting of axons, specification of visual cortex, and correlates of the critical period. Encompassing technical advances in cellular and molecular biology and in video imaging and microscopy, contributions in each of these areas provide new information at the cellular and molecular levels to complement the now classic descriptions of visual development previously available at the level of neural systems.ContributorsKaren L. Allendoerfer, David M. Altshuler, Antonella Antonini, Seymour Benzer, Edward M. Callaway, Constance L. Cepko, Hollis T. Cline, Max S. Cynader, N. W. Daw, Scott E. Fraser, K. Fox, Eckhard Friauf, Anirvan Ghosh, R. W. Guillery, William A. Harris, Christine E. Holt, Lawrence C. Katz, Susan McConnell, Pamela A. Raymond, Thomas A. Reh, Carla J. Shatz, Michael P. Stryker, Claudia A. 0. Stuermer, Mriganka Sur, David L. Turner, T. N. Wiesel

This book provides a series of comprehensive views on various important aspects of vertebrate photoreceptors. The vertebrate retina is a tissue that provides unique experimental advantages to neuroscientists. Photoreceptor neurons are abundant in this tissue and they are readily identifiable and easily isolated. These features make them an outstanding model for studying neuronal mechanisms of signal transduction, adaptation, synaptic transmission, development, differentiation, diseases and regeneration. Thanks to recent advances in genetic analysis, it also is possible to link biochemical and physiological investigations to understand the molecular mechanisms of vertebrate photoreceptors within a functioning retina in a living animal. Photoreceptors are the most deeply studied sensory receptor cells, but readers will find that many important questions remain. We still do not know how photoreceptors, visual pigments and their signaling pathways evolved, how they were generated and how they are maintained. This book will make clear what is known and what is not known. The chapters are selected from fields of studies that have contributed to a broad understanding of the birth, development, structure, function and death of photoreceptor neurons. The underlying common word in all of the chapters that is used to describe these mechanisms is “molecule”. Only with this word can we understand how these highly specific neurons function and survive. It is challenging for even the foremost researchers to cover all aspects of the subject. Understanding photoreceptors from several different points of view that share a molecular perspective will provide readers with a useful interdisciplinary perspective.