The overall objective in this project is to investigate the control mechanisms involved in the formation of cell surface during the regeneration of cilia in Tetrahymena. We are isolating and identifying surface membrane proteins and are studying their turnover in morphostatic cells as well as investigating their synthesis in cells in the process of regenerating cilia. Phospholipid synthesis is being studied using the incorporation of 32P into cellular phospholipid, and protein synthesis is being studied in double labeling experiments using 3H -leucine and 14C -leucine. Surface probes are also being used to determine whether non-ciliary surface membrane migrates into the newly formed ciliary membranes during ciliary regeneration. Membrane regression can also be controlled by Tetrahymena. Studies of the synthesis and migration of membrane components during regeneration coupled to regression are expected to contribute to our understanding of the general mechanisms involved in the control of surface membrane biogenesis in this cell type.