+-------------+----------+------+--------+------+--------+-----+-------+ The proportion of single-combed offspring in the total filial population is 30.0 per cent, a departure of such magnitude from the expected 25 per cent as to arrest our attention. Further inspection of table 9 shows that the excess of single-combed offspring is found only in the lower half of the series. When the percentage of median element in the parents is under 50 the proportions of I, Y, and no-median combs are as 25.5 per cent, 49.8 per cent, 24.7 per cent, or close to expectation; but when the percentage is 50 or over the proportions are, on the average, 33.6 per cent, 45.2 per cent, and 21.2 per cent, a wide departure from expectation, 1108 individuals being involved. An examination of table 9 shows, moreover, that the proportion of offspring with single comb rises steadily as the proportion of the median element in the parentage increases from 50 per cent. The meaning of this fact is at present obscure, but the suspicion is awakened that, while the "cup comb" and the more deeply split combs are typical heterozygotes the slightly split combs are a complex of 2 or more units, one of which is "single comb." But that this is not the explanation follows for two reasons: first, that even in the F1 generation slightly split combs are obtained, and, second, that the offspring of the cup combs are much more variable than those of slightly split combs (70 to 90 per cent median). What is strikingly true is that, from 50 per cent up, as the proportion of the median element in the parents increases the percentage of single-combed offspring rises. The matter may be looked at in another light. Median comb is dominant over its absence. Typically, we should expect F1 to show a single comb; the Y comb that we actually get is a heterozygous condition due to the failure of the median comb to dominate completely. Typically we should expect F2 to reveal 75 per cent single combs, of which 1 in 3 is homozygous and 2 in 3 are heterozygous. Owing to the failure of single comb always to dominate completely in the heterozygotes, we expect to find some of the 75 per cent with the Y comb. When in the parents dominance has been very incomplete in the heterozygote (as is the case in the 0 per cent to 40 per cent median-combed parents) we find it so in the offspring also and all heterozygotes show a Y comb of some type. But when in the parents dominance has been strong in the heterozygote (50 per cent to 90 per cent) it is so in the offspring also and only a part of the heterozygotes show the Y comb; the others show the single comb and thus swell the numbers of the single-combed type. The only objection to this explanation is found in the reduction in the percentages of the no-median type. Thus, adding together the homozygous and heterozygous median-combed offspring and comparing with the non-median-combed, we find these ratios: