DISTRIBUTION OF GANGLION-CELLS AND OBJECT LOCALIZING ABILITY IN THE RETINA OF 3 CETACEANS

The distribution of ganglion cells was examined in the retina of three cetacean species: the false killer whale, the pacific white-sided dol phin and the beluga. Three parameters of vision were estimated from th e distribution of ganglion cells, i.e., the retinal resolving power (v isual acuity), the field of best vision, and the direction of visual a xis. In these three species, the retinal resolving power was 2.6-3.3 c ycles per degree, the width of held of best vision was 12.8-15.4 degre es, and the direction of visual axis was 51-68 degrees from the geomet ric center of the retinal hemisphere. Interspecific differences are sm all, and these parameters are similar among most marine cetaceans. How ever, there are many differences in these parameters between marine ce taceans and terrestrial mammals.