Bistratified amacrine cells in the retina of the tammar wallaby--Macropus eugenii.

Cajal (1911) noted that bistratified amacrine cells were common in non mammalian species and extremely rare in the mammalian retina. An examination of the marsupial retina of the tammar wallaby, stained with a modified Golgi procedure, revealed that a particular type of bistratified amacrine was frequently impregnated with the silver stain. Flat mount and transverse sections showed that the morphology of this cell did not correspond with any of the species-dependent bistratified amacrines reproduced in Cajal's drawings. Instead, the cell appeared to be almost identical to the AII or rod amacrine that has been observed in a number of mammalian retinas. The relative frequency with which the cell appears in our material, and its confirmed rod input in other species, are both consistent with the grazing habits of the tammar wallaby which is a crepuscular animal that does most of its feeding at dusk and after dark.