This volume contains the lectures given at the NATO Advanced Study Institute on "Biophysics of Photoreceptors and Photomovements in Microorganisms" held in Tir renia (Pisa), Italy, in September 1990. The Institute was sponsored and mainly funded by the Scientific Affairs Division of NATO; the Physical Science Committee and the Institute of Biophysics of National Research Council of Italy also supported the School and substantially contributed to its success. It is our pleasant duty to thank these institu tions. Scientists from very different backgrounds contributed to the understanding of this fast developing field of research, which has seen considerable progress during the last years. The areas of expertise ranged from behavioral sciences, supported by sophi sticated techniques such as image analysis or laser light scattering, to spectroscopy, ap plied, in different time domains, to the study of the primary photoreactions, to electro physiology, biochemistry or molecular biology, with the aim of analyzing the various steps of the transduction chains and how they control the motor apparatus of the cells. The organisms studied covered a wide range, from bacteria to algae, fungi and other eukaryotes. Thus, the ASI represented a successful opportunity for carrying on and imple menting an interdisciplinary approach to the study of the biophysical basis of photore ception and photosensory transduction in aneural organisms, with special attention to the basic phenomena and the underlying molecular events. We hope that this book has caught the spirit in which the ASI was conceived."

This book is based on the lectures given at the NATO Advanced Study Institute on "Sensory Perception and Transduction in Aneural Organisms" held in Volterra (Pisa. Italy) from the third to the fourteenth of September. 1984. The Advanced Study Institute was planned as a high level course dealing with several aspects and problems of sensory perception and transduction of diverse environmental stimuli in aneural organisms. Scientists from different fields and cultural backgrounds were present at the meeting. both as lecturers and as students. The lectures and the discussions that followed represented a well integrated interdisci plinary approach to the questions considered. At the end of the Advanced Study Institute course. it was quite clear that. notwith standing the apparent heterogeneity of the topics dealt with. unifying concepts and ideas already existed, among the most important being the role of membranes and their physicochemical properties. All this should be reflected in the content of this book. We gratefully acknowledge the financial sponsorship of the Scientific Affairs Division of NATO (Brussels), that made both the Advanced Study Institute on "Sensory Perception and Transduction in Aneural Organisms" and this book possible. Finally. we are also indebted to Ms. Pat Parham Morgan who expertly retyped all the chapters of the book and Ms. Leslie Schmidt of Plenum Publishing Co. provided us valuable advice and suggestions on the preparation of this book. G. Colombetti F. Lenci P. S."