No more than a fish loves water. - Is not this a strange fellow, my lord, that so confidently seems to undertake this business, which he knows is not to be done; damns himself to do, and dares better be damn’d than to dolt? All’s Well That Ends Well Act III, Sc. 6 This volume is the direct result of a NATO-Advanced Study Institute of the same title. held at Bishop’s University, Lennoxville, Quebec, Canada, August 1974, under the joint sponsor ship of the NATO-Scientific Advisory Committee, National Research Council of Canada and the Universite de Montreal. It is not, however, strictly restricted to the lectures and seminars pre sented at the ASI. Contributions have been included from two workers who found at a fairly late stage that they could not attend and also included are a table giving the visual pigments and an other dealing with the distribution and development of retinomotor responses. I encouraged the authors to prepare speculative reviews highlighting their own research or that of their immediate col leagues and a number of them have done so. Several contributors, notably those who were asked to give lectures of a general nature at the ASI have written reviews of somewhat greater scope. The result is a collection of papers representing a great variety of approaches to the study of vision in fishes.