The papers published in this Volume are the fruits of a symposium held in Regensburg in April 1987. The meeting was held to com memorate two most significant events in the development of com pound eye research. In chronological order these are firstly, Sigmund Exner's seminal monograph on the physiology of compound eyes of crustaceans and insects, which was first published in Vienna in 1891, and is now shortly to appear for the first time in the English translation Exner, S. (1989) The Physiology of the Compound Eyes of Insects and Crustaceans. Springer Berlin Heidelberg New York Tokyo]....

Exner's classic monograph describes the basic optical mechanisms in operation in compound eyes and, despite the passage of time, still remains a definitive work. Although his findings were seriously questioned during the modern revival of interest in compound eyes, all his major discoveries have now been validated. The principle of the lens cylinder and the elucidation of the mechanics of apposition and superposition optics are amongst his outstanding contributions. It also includes a broad survey of the optics and anatomy of the eyes of many insect and crustacean species, and the first...