Comparative analysis of the functional and morphological characteristics of the central nervous system of extant vertebrates can shed light on the evolutionary forces that have shaped different vertebrate brains, which, although sharing similar elements and a basic plan, have had to cope with extremely diverse environments. We chose the Didelphis opossum as an experimental model because of its putative resemblance to cretaceous mammals. This marsupial can be quite accurate in performing activities that rely on visual skills. The existence of an oculomotor system that stabilizes the image on the opossum's retina is of primary importance, compensating for movements of the head and providing this species with a framework to stabilize the retinal image while foraging for food. We review evidence for how the nucleus of the optic tract, a key structure involved in this function, is organized to provide an appropriate blending of form and function to bring about this basic behavior.