This volume or1g1nates from a NATO Advanced Study Institute on "Photoreceptors" dedicated to M.G.F. Fuortes, held in Erice 1-12 July 1981. The lectures given at the course provided a general review of the photoreceptors functions in both vertebrate and inver tebrate eyes. Elaborating on the most recent hypotheses the lec tures also added new and interesting details. In order to preserve the novelty and freshness of the subject matter and thus ensure the usefulness of the volume, the authors in their written contributions emphasize more specific findings of their current research rather than the tutorial nature of the lectures actually presented. The contributors of this volume wish to dedicate their papers to the memory of Mike Fuortes, who has been for many of them an inspiring collegue and friend. Five papers that do not strictly pertain to the topics of the course are also included in the volume, the authors could not attend the meeting, but wanted to contribute an article to this memorial volume."

Present knowledge of the mechanisms underlying any single sensory modality is so massive as to discourage effort directed towards completeness. The idea underlying the structure of this volume on "Sensory transduction" was to select just a few topics of general interest, which are currently being investigated and for which a reasonably clear picture is now available. During the last five years there has been a revolution in the way sensory physi ologists think about transduction, and a series of exciting advances have been made in understanding the basic processes of photo transduction, chemotransduction and mechan otransduction. It is clear that in many cases the fundamental processes by which nature attains optimization of performance are similar, and that they have much in common with more general processes of signal recognition by living structures. The molecular events underlying the detection of photons by visual cells, the recognition of a given molecule by a chemoreceptor, or the level of a hormone in the extracellular fluid by a target cell, are all very similar, and involve the activation of a sequence of events leading to a secon d messenger. The 20 papers that form the present volume cover various topics in the field of sensory transduction. They originate from the lectures, seminars and discussions which made up the XVIII Course of the International School of Biophysics held in Erice, 9th - 19th June 1988.

This volume derives from papers presented at the 4th biennial meeting of the Italian Biophysical Society, held in Parma in October 1979. It includes review lectures presented by guest scientists (R.H. Adrian, E. Neher, S. Ottolenghi, and G. Zaccai); the remaining reviews and papers present some of the problems currently under study in our country. One can see that biophysical problems are studied under differ- ent academic roofs, i.e., at physiological or biochemical departments. We consider this a strength and a weakness at the same time. The "Italian Bioenergetics Group" contributed to the success of the meeting, as much as the groups working in various laboratories of the Consiglio Nazionale delle Ricerche, in particular those of the National Group of Cybernetics and Biophysics. To them, and to the University of Parma, which contributed financial and organiza- tional support, the Editors of this volume wish to express their appreciation. Particular thanks are to Drs. E. Carbone and V. Lenci, who spent time and effort for the meeting and in collecting the papers. The special care in the typing goes to the credit of Miss Rampello, to whom the Editors express their deepest gratitude.