We have tested the hypothesis that the leading edge of the growing Drosophila compound eye acts as a template that organizes unpatterned cells of the retinal epithelium into the accurate cellular mosaic of the eye. Unpatterned fragments of the epithelium, not containing the leading edge of the growing field, were transplanted into larval hosts. After hosts pupated, the implants were recovered; most contained ommatidia, demonstrating that the leading edge of the growing eye pattern is not required for its propagation. In a second set of experiments, implants were recovered before hosts pupated and examined for ommatidia using a monoclonal antibody. These implants likewise differentiated ommatidia and the temporal progress of retinal development in the implants mirrored that of normal development. A schedule of ommatidial development thus appears to be mapped onto the retinal epithelium in advance of the leading edge.