This ongoing research program involves behavioral, physiological, and anatomical studies of vision in species which have either highly cone-dominated or highly rod-dominated retinas. Among the former are ground squirrels and tree squirrels; among the latter are flying squirrels, rats, and Aotus monkey. The projects to be carried out include: (a) a determination of spectral sensitivity and color vision in the antelope ground squirrel; (b) measurement of spatial and temporal sensitivity in squirrels; (c) a determination of the functional role of the small number of rods found in the cone-dominated visual system; (d) a determination of the functional role of the small number of cones found in the rod-dominated visual system; (e) an electrophysiological investigation of the response properties of single cells in the squirrel visual system; (f) an evaluation of possible intraspecies variation in retinal anatomy and function in the ground squirrel; (g) an examination of the functional consequences of extreme photic environments; (h) a characterization of spectral sensitivity, color vision, and spatial vision in the Aotus monkey.