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.

Inhalt
Interaction between Light and Matter.- Receptor Pigments in Light-Induced Behavior of Microorganisms.- Sensitization of the Visual Pigment in a Photoreceptor.- In Vitro Regeneration of Visual Pigment in Isolated Vertebrate Photoreceptors.- Retinal Binding Protein in the Honeybee Retina.- Early Steps in the activation of Photoreceptor Enzymes by Light: Interaction between Disk Membrane Proteins Triggered by Light and Regulated by G.T.P.- Intracellular Changes of H+ and Ca2+ in Balanus Photoreceptors.- Light-Induced Voltage Fluctuations in Barnacle Photoreceptors.- The Early Receptor Potential: its Mode of Generation, Application to Study of Photoreceptors, and Functional Significance.- Some Basic Information about the Light Response of Frog Rods.- Recovery from Light-Desensitization in Toad Rods.- Ionic Currents Activated by Voltage and by Intracellular Calcium: A Voltage Clamps Study in Solitary Vertebrate Photoreceptors.- Regenerative Photoresponses in Toad Rods.- Synaptic Responses of Retinal Photoreceptors.- Microtubules in Vertebrate Photoreceptors.- A Quantitative Study on Synaptic Ribbons in the Photoreceptors of Turtle and Frog.- A Note on the Synaptic Events in Hyperpolarizing Bipolar Cells of the Turtle's Retina.- Quantitative Morphology of Amacrine Cells in Teleost Retina.- Chromatic Organization and Sexual Dimorphism of the Fly Retinal Mosaic.- Visual Control of Flight in the Fly.- Contributors.