BRACHYDACTYLY IN THE FOWL 109 
TABLE 1 
A summary of the data arranged to show the relation between brachydactyly 
polydactyly, booting and comb form in the eighty-six 
living chicks 
A. BRACHYDACTYLY AND D. BRACHYDACTYLY AND 
COMB FORM POLYDACTYLY 
Broad comb Narrow comb Five toes Four toes 
Obs. Exp. Obs. Exp. Obs. Exp. Obs. Exp. 
Shontmounth toe... 2-54. 15 15e5 16 15e5 10 10 21 21 
Monestourth tev... +... .4.4)) 28 DAL ® Dal 1 ies) 18 17.9 37 347/01 
B. POLYDACTYLY AND E. POLYDACTYLY AND 
COMB FORM BOOTING 
Broad comb Narrow comb | Booted shank | Smooth shank 
Obs. | Exp. | Obs. | Exp. | Obs. | Exp. | Obs. | Exp. 
TRINVEATE Ss Oo ete See eee 16 14 12 14 13 pes 15 | 16.2 
HOMERGOCS Hearne ao. teas Pal 29 31 29 23 24.2 35 | 33.8 
Cc. BOOTING AND COMB F. BOOTING AND BRACHY- 
FORM DACTYLISM 
Broad comb Narrow comb |Short fourth toe|Long fourth toe 
Obs. | Exp. | Obs. | Exp. | Obs. | Exp. | Obs. Exp. 
DOoLed Shakes a .2c)225...| AT 18 19 18 dl 12.9 iy | aye 
Smooth shank.............| 26 25 24 25 Osieis 50 | 32 
accompanying table (table 1, A—F), which is based on the 86 
chicks hatched. Since the male used was, in Mendelian terms, 
heterozygous for all four of the peculiarities studied, the de- 
terminers for each (with the partial exception of comb form) 
having been supplied by his paternal gamete alone, and since 
the females were homozygous for the absence of all these 
characters, an especially favorable opportunity was afforded for 
testing linkage relations. If each character behaved in a 
strictly Mendelian fashion and segregated independently, the 
expected value for each combination would be 21.5, and the 
sum of each pair added either vertically or horizontally would 
be 43. While, as already indicated comb form agrees exactly 
with the Mendelian expectation (43: 43 for those that hatched) 
