Origins of crossed and uncrossed retinal projections in pigmented and albino mice

The extent of the binocular cortical field in albino mice, as revealed by recording from single cells, was almost normal; although the input from the ipsilateral eye was weaker than normal, most cells were driven from both eyes. By backfilling retinal ganglion cells from one optic tract with horseradish peroxidase we examined the origins of the retinofugal projections. Filled cells ipsilateral to the injected tract were concentrated in a crescent‐shaped area bordering the inferior temporal retina. In black mice this area constituted 20% of the total retinal area, in albinos 17%. In black mice we counted nearly 1,000 labeled cell in the ipsilateral retina, or 2.6% of all cells filled in both eyes. Albinos had about one‐third fewer filled cells ipsilaterally than black mice. Four percent of all ipsilaterally filled cells in black mice and 8% in albinnos were scattered outside of the crescent region. The density of ipsilaterally projecting cells was uniform throughout the crescent region in black mice, but decreased toward the central retina in albinos.