I propose to study the morphology of retrogradely labeled gaglion cells in retinae of cats, ferrets, New World monkeys (Saimiri sciureus), and Old World monkeys (Macaca fasicularis) following small electrophoretic injections of horseradish peroxidase (HRP) into regions of the brain that receive retinal afferents. The development of the morphology and radial orientation of the dendritic fields of retinal gaglion cells in cats, ferrets, New World monkeys and Old World monkeys will also be studied. In addition, the dedritic field morphologies and receptive field properties of functionally identified retinal gaglion cells will be studies in cats. Finally, I will determine whether the systematic relationship between preferred orientation and receptive field position found in cat visual cortex is also found in striate and extrastriate cortes of primates. The experiments will be carried out using histochemical procedures.which stain the cell bodies, axons and dendrites of gaglion cells labeled by extracellular and intracellular injections of horseradish peroxidase. The receptive field properties of visual neurons will be studied using standard extracellular and intracellular single unit recording procedures and a computerized optical display. Neuronal structure will be studies using a computerized morphometry system. These studies will help to (1) develop a morphological classification of retinal gaglion cells in the cat a monkey which can be related to the functional classification of different classes of retinal gaglion cells in these species, (2) determine which aspects of retinal gaglion cell morphology are responsible for the orientation sesitive response of retinal ganglion cells, and (3) clarify how dedritic field morphology and orientation develops in the retina and affects the organization of visual cortex