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Abstract
A comparative study was made of the fine structure of Mailer's cells in various vertebrates. In those species with vascular retinas (cat, rat, and opossum), the organelles in the cytoplasm of the Müllerian cells were extremely scanty in the outer layer, but more numerous vitread to the inner nuclear layer of the retina. The microvilli were relatively few. When there was a supraretinal vascular membrane in the vitreous (frog, carp, Fundulus, and bowfin), distribution of organelles in the Müllerian cell cytoplasm was similar to that in the vascular type of mammalian retina. The cytoplasm of the Müllerian cells in avascular retinas (rabbit, pigeon, lizard, turtle, Necturus, and dogfish) had many mitochondria, occasional Golgi apparatus, and microvilli were numerous around the base of the inner segments of the photoreceptor cells. Many glycogen particles were scattered throughout the cytoplasm of Müllerian cells in the avascular retina, expecting in bird and lizard, but were somewhat less in the Müllerian cells in vascular retinae. Arrangement of nuclei of Müllerian cells varied depending on the location of the amacrine cells. The external limiting membrane was composed of zonulae adhaerentes in many species, but in a few (frog, carp, and Fundulus), there were extensive gap junctions between Müllerian cells in addition. In the carp retina, desmosomal connections (macula adhaerens) were also found forming part of the external limiting membrane. In reptiles, a peculiar apparatus, consisting of a network of dense filamentous material occurred in the cytoplasm of the Müllerian cells at the level of the external limiting membrane.