This volume is a collection of contributions from the 47th Annual Symposium of the Society of General Physiologists, held September 8-11, 1993 at the Marine Biological Laboratory in Woods Hole, Massachusetts. The Symposium brought together scientists who study cytoskeletal and membrane functions with scientists whose research is focused on molecular evolution or on mechanisms that generate genetic diversity. The theme for the symposium reflects a revolution in the study of cellular physiology.