Contents

16 July 1976
Vol 193, Issue 4249

About The Cover

Coloration of gibbons. Pileated and lar gibbons have white hands and feet. Concolor gibbons shown are from Laos; males farther east are entirely black. Borneo is divided between two species of entirely different voice but having similar polymorphic coloration in endless variety. Arrows connect taxa with the same female song. See page 235. [Painting by Joe T. Marshall, Jr., U.S. Army Medical Component, SEATO]