It is now generally accepted for a variety of reasons - morphological as well as physiologica- that the visual systems of arthropods provide a suitable model for the study of information processing in neuronal networks. Unlike the neurophysiology of the visual pathway in the frog and the cat which is more than adequately documented, recent work on the compound eye and optical ganglia of spiders, crustaceans, and insects has scarcely been summarized. In order to fill this void so that others, especially vertebrate neurophysiologists may become familiar with the advantages of these systems, our group at Zurich University organized here in March 1972, a European meeting to discuss the anatomical. ! neurophysiological and behavioral knowledge on the compound eye and the visual. pathway of arthropods. Systems analysis was regarded as the main theme of the conference, but systems analysis of a network of neurons cannot be done as a mere "black-box" maneuver. The conference therefore tried to reconcile neurophysiology and behavioral analysis in order to make predictions about a necessary and sufficient neural structure. The "wiring dia­ grams" of such a structure might then be confirmed histologically. Hence the aim of the conferen­ ce was not to deal only with the structure and function of the compound eye - i. e.