Figure 10. Geometry of ROS discs. A shows model of amphibian disc used for computing the effect of disc incisures on the rate of rhodopsin diffusion. Shaded wedge-shaped areas show geometry of bleaching and measuring beam in the microspectrophotometer. L denotes the ROS diameter, and x is the coordinate, as in Equation (2). B shows scheme of the grid for finite-difference solution of two-dimensional diffusion equation for the structure depicted in A. Shaded area is covered by the bleaching flash. Heavy lines delineate the borders at which the diffusion fluxes are set to 0. C shows schematic of the cross-section of Tokay gecko ROS based on our electron microscopy data. The arrow points to longitudinal cytoplasmic channel that started at the connecting cilium and ran along the entire length of the outer segment. Incisures radiated from the channel and separated the discs into a few isolated lobes.