A light microscopic study of the bifoveate retina in the lizard Anolis carolinensis: General observations and convergence ratios

Abstract The bifoveate all cone retina of the lizard Anolis carolinensis was examined under light microscopy in this study using toluidine blue and Golgi staining techniques. Photomontages of sections through the retina were divided into counting corridors on the basis of the paths of connectivity of the retinal cells. Counts of receptors and ganglion cells were made, and the convergence ratio between them was determined. This ratio was found to be relatively constant across the retinas (1.33 in horizontal sections, 1.42 in vertical sections) except in the foveola where there was a circumstribed dip in its values. There was also a slight decrease in the convergence ratio in the shallow temporal fovea relative to surrounding retina. The concept of convergence ratio and the possible relevance of these observations to theories of deep foveal function are discussed.

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