Dr. Masland is the Charles A. Pappas Professor of Neuroscience at Harvard Medical School and Neurophysiologist in Neurosurgery at Massachusetts General Hospital, Boston. He received his A.B. degree from Harvard College and his Ph.D. degree from McGill University. His postdoctoral work was done at Stanford and Harvard Medical Schools. Among his awards is Harvard University's Hoopes Prize, for excellence in teaching. Research in this laboratory concerns local cellular interactions within the retina. Mammalian retinas contain a surprising diversity of cell types. Amacrine cells, upon which we have especially concentrated, exist in atleast 20 different morphological subclasses. By fluorescent staining many of these classes can be visualized by distinct, reproducible populations in histological material or intact retinas in vitro during electrophysiological recording. The broad questions under investigation are: (1) why this diversity exists, i.e., what functions the many cells carry out; (2) how orderly structural relations among the cells are created and maintained; and (3) how inner retinal cell's local dendritic networks function.