Wilson — Unsound Mendelian J)evelo2wients. 403 



hornless, and white-faced, 9 ; black, horned, and white-faced, 9 ; black, 

 horned, and black-faced, 3 ; red, liornless, and red- faced, 3; red, horned, and 

 white-faced, 3 ; red, horned, and red-faced, 1. According to the formula 

 there are three pairs of characters concerned in the case. The three dominants 

 are exhibited in the group of twenty-seven, two dominants and the third 

 recessive in each group of nine, one dominant and the two remaining 

 recessives in each group of three, and the three recessives in the group of 

 one. lu each group of nine the recessive which is shown is the alternative 

 of the dominant which is not shown. In each group of three the dominant 

 which is shown is the alternative of the recessive which is not shown. Thus 

 the three dominants in this case are blackness, liornlessness, and white-face, 

 while their three corresponding recessives are redness, hornedness, and normal 

 face : normal face being that in which the face colour is the same as that of 

 the body. As in the previous cases, there is no difficulty in identifying the 

 characters and the nature of the factors to which they are due. That being 

 so, we may set down this case, just as the typical one for three pairs of 

 characters was set down, with letters indicating the characters concerned 

 instead of the unknowns, XxYi/Zz. 



B = black. r = red. 



P = hornless or polled. h = horned. 



W = wliite-faeed. ii = normal-faced. 



To make the descriptions of the groups clearer we shall range them 

 across the page thus : — 



21 B P W : Black, polled, white-faced. 

 9 B P n : Black, polled, normal-faced. 

 Eed, polled, white-faced. 

 Black, horned, white-faced. 

 Black, homed, normal-faced, 

 red, polled, normal-faced, 

 red, horned, white-faced, 

 red, horned, normal-faced. 



But many eases have been found since the Mendelian method of analysis 

 came into use in which the interacting characters have been difficult to 

 identify. One of the first was that of fowls' combs. When rose and single 

 combs were mated the first crosses were all roses, and the second crosses roses 

 and singles in the ratio 3:1; and, when pea and single combs were mated, 

 the first crosses were all peas, while the second crosses were peas and singles 

 in the ratio 3:1. From this it was inferred that the rose and pea combs 



