The Alleged Charm of Disparity in Sexual Attraction--The Admiration for High Stature--The Admiration for Dark Pigmentation--The Charm of Parity--Conjugal Mating--The Statistical Results of Observation as Regards General Appearance, Stature, and Pigmentation of Married Couples--Preferential Mating and Assortative Mating--The Nature of the Advantage Attained by the Fair in Sexual Selection--The Abhorrence of Incest and the Theories of its Cause--The Explanation in Reality Simple--The Abhorrence of Incest in Relation to Sexual Selection--The Limits to the Charm of Parity in Conjugal Mating--The Charm of Disparity in Secondary Sexual Characters. When we are dealing with the senses of touch, smell, and hearing it is impossible at present, and must always remain somewhat difficult, to investigate precisely the degree and direction of their influence in sexual selection. We can marshal in order--as has here been attempted--the main facts and considerations which clearly indicate that there is and must be such an influence, but we cannot even attempt to estimate its definite direction and still less to measure it precisely. With regard to vision, we are in a somewhat better position. It is possible to estimate the direction of the influence which certain visible characters exert on sexual selection, and it is even possible to attempt their actual measurement, although there must frequently be doubt as to the interpretation of such measurements. Two facts render it thus possible to deal more exactly with the influence of vision on sexual selection than with the influence of the other senses. In the first place, men and women consciously seek for certain visible characters in the persons to whom they are attracted; in other words, their "ideals" of a fitting mate are visual rather than tactile, olfactory, or auditory. In the second place, whether such "ideals" are potent in actual mating, or whether they are modified or even inhibited by more potent psychological or general biological influences, it is in either case possible to measure and compare the visible characters of mated persons. The two visible characters which are at once most frequently sought in a mate and most easily measurable are degree of stature and degree of pigmentation. Every youth or maiden pictures the person he or she would like for a lover as tall or short, fair or dark, and such characters are measurable and have on a large scale been measured. It is of interest in illustration of the problem of sexual selection in man to consider briefly what results are at present obtainable regarding the influence of these two characters.