Sex Differences in Colour Vision

IN a previous communication1, it was shown that women with known colour-blind relatives were significantly more often red-green weak to a slight extent than women taken at random. This carried the implication that red-green blindness must be an incompletely recessive Mendelian character (although sex-linked), because a large proportion of the women with known colour-blind relatives must be heterozygous for that defect. Several later experiments have confirmed that conclusion, essentially the same results .being obtained with each new group tested.