Experiments are presented which will examine the general nature of disc membrane synthesis and the function of this membrane once assembled in the photoreceptor outer segment. An in vitro system employing radioactive precursors for biochemical and autoradiographic analysis will be used to study: (1) the biosynthesis of visual pigment and its renewal in rods and cones, (2) the nature of visual pigment in the inner segment and the site of chromophore addition, (3) the metabolism of the photoreceptor cell and the interrelationships between lipid and protein synthesis, (4) the role of the pigment epithelium in regulating both photoreceptor metabolism and visual pigment regeneration, and (5) the presence or absence of rhodopsin in the plasma membrane. Particular attention will be given to the role of phospholipids in affecting membrane growth and function. The mono- and polyphosphoinostitides of the retina and outer segment will be examined to determine their possible role in ion regulation, transduction or adaptation. Finally, the scanning electron microscope will be applied to these problems using the attached spectrometer in a manner similar to the techniques of electron microscope autoradiography. These experiments will hopefully lead to both a basic knowledge of the nature and function of a biological membrane as well as a better understanding of the visual process.