BRACHYDACTYLY IN THE FOWL 112 
in a certain percentage of cases, the frequency depending on the 
distances of the two determiners from each other. There “is 
some evidence that could be regarded as favoring this inter- 
pretation. Five chicks with more or less booted tarsi (grades 1, 
1, 1, 1, 2) were not brachydactyl. If these represented true 
cases of ‘crossing over’ there should have been an equal number 
of brachydactyl chicks. which were not booted. One specimen 
was obtained. To fully substantiate this hypothesis it would 
Fig. 5 Curve showing the relation between brachydactyly and booting in 
86 living chicks. Each square represents an individual, the shaded ones being 
booted. The indices of brachydactyly are indicated below. 
be necessary by further breeding experiments to derive from the 
same hybrid stock one strain with feathered feet and long toes 
and another strain with unfeathered feet and short toes. 
In this connection it was thought desirable to investigate 
the relation of these characters in other species. The writer is 
greatly indebted to Mr. Louis Agassiz Fuertes for carefully 
examining for him a large number of booted grouse, ptarmigans, 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 25, NO. 2 
