My research associate (Jean Brandenburger), summer colleague (Colin Hermans), and I study the fine structure of photoreceptors in animal phyla not yet well explored, further our efforts to determine the effects of light and darkness on the ultrastructure of light-sensitive cells, continue our investigation of the function of unique 800 A vesicles in the photoreceptoral cells of molluscan eyes, analyze membrane turn-over in the eyes of a snail, and seek evidence on the localization of vitamin A in the retina of that snail.