Postembryonic development of the visual system of the locust, Schistocerca gregaria. II. An experimental investigation of the formation of the retina-lamina projection.

In the compound eye of the locust, Schistocerca gregaria, neurons from the retina project to the lamina in a precise topographical mapping. The formation of this projection was investigated in grafting experiments which altered the spatial or temporal relationship between the retina and the lamina. The results show that retina axons tend to grow along the paths of adjacent axons, with no indication of specificity for their normal termination sites. It is suggested that the orderly sequence of retina differentiation during normal development plays a major role in imposing pattern both upon the developing projection and, through some form of inductive interaction between retina and lamina neurons, upon the lamina.