The development of embryonic retinoblasts into phenotypically mature Müller glial cells has been shown to be dependent on close juxtapositional relationships between heterotypicells of the retina. In this report, I review experiments in which we have attempted to examine the role of actual cell contact in the regulation of biochemical differentiation of retinal glial cells. Probes which bind to cell surface components including antibodies to the retina cell membrane and plant lectins were tested for their ability to interfere with normal histogenesis and glial maturation in a reaggregation-basedin vitro development assay. Data are discussed which show that antibodies to the cell surface and the succinylated derivative of the plant lectin concanavalin A can markedly impair both histogenesis and glial maturation potential if introduced into cultures of reaggregating dissociated embryonic retina cells. Preliminary analyses of membrane components which react with the lectin have been performed. The results suggest that certain specific membrane glycopeptides are expressed by dissociated retina cells in an age-dependent manner. Also, the results show that decline in the ability of the embryonic cells to elaborate these surface components correlates with the capacity of the cells toreform developmentally regulatory neuronal-glial communication “linkages”