ONE FIQURE
Based on comparative and experimental studies of the laminar organization and the afferent fiber connections of the dorsal nucleus of the lateral geniculate body (for brevity, the term lateral geniculate is used later in this report), Le Gros Clark has proposed a possible central mechanism for color vision ('40, '42, '47, '49). I n rhesus monkey there are two sets of triple-fiber conducting systems, one from each retina, terminating at each lateral geniculate (Glees and Clark, '41). The latter consists of 6 laminae at its central portion, which fuse into 4 and then into two toward the periphery (Clark, '41a, b). Le Gros Clark suggested that a single pair of laminae, one of which receives the optic fibers from the temporal half of the ipsilateral retina, the other from the nasal half of the contralateral retina, subserves one primary color. The 6-laminar portion of the lateral geniculate may provide the neural substratum for trichromacy in higher primates central vision. The four-laminar and two-laminar parts may correspond to the dichromatic and monochromatic vision in the peripheral fields (Clark, '49). I n support of this suggestion, he reported selective degeneration, mainly in the first magnocellular layer, in the lateral geniculates of two monkeys (out of three) that were kept about one month in red light ( '43). This finding suggests that the magnocellular layers may mediate blue color vision. Since the lateral geniculates of one monkey showed no disuse atrophy, and the degen-