The heredity of the relative numbers of red and green receptors in the human eye

SummaryThe relative numbers of red and green cones in the human eye have been determined by an analysis of various luminosity curves. These ratios show large variations; in extreme cases one of the cones is missing (colourblindness). It is found that this ratio depends on a sex linked factor. (This was known already for colourblindness). For women the ratio proves to be the mean value of the ratios which would be caused by the two factors alone. This rule explains the wellknown heredity of colourblindness for women.