Fig. 3. Rhabdomere volumes of receptor cells near the center of the retina. (A) Light micrograph of longitudinal section showing two retinulae. bm, basement membrane; ne, nuclei of elongate photoreceptors; np, nucleus of small proximal receptor; r, rhabdom; t, tracheoles; te, tracheole ends. (B) Rhabdomere volumes, calculated from 21 virtual sections (see Materials and methods and Fig. 1A) of photoreceptors in relation to depth of retina. Each rectangle represents a virtual section: its vertical side represents the section thickness; the horizontal side represents the area of the rhabdomere. The calculated rhabdomere volume for each cell type is indicated.