BULLETIN 232. 



THE HISTOLOGICAL BASIS OF THE DIFFERENT 

 SHANK COLORS IN THE DOMESTIC FOWL.* 



By H. R. Barrows. 



In this laboratory studies on the inheritance of various char- 

 acters in poultry have been in progress for some time. Among 

 other characters which have been dealt with from this point of 

 view is the color of the shank (lo), (ii).t In connection with 

 this work on inheritance, the question arose as to what histo- 

 logical conditions are associated with the different shank colors 

 observed in fowls. As is common knowledge, shank colors, like 

 other characters vary with the breed. Among the shank colors 

 commonly occurring in Gallus, and observed in the breeding 

 work here are : white, yellow, blue, black, green, black over 

 green, black over white (dusky), black over yellow (dusky), 

 black over white (dense), black over yellow (dense), black over 

 blue, blue under white, pink, and red. These colors and varia- 

 tions may, in part, appear in individual scales as well as in the 

 shank as a whole. The problem was to determine for each of 

 the above markings the following points : 



1. The color of the ultimate pigment granules. 



2. Their general nature — whether fatty oils (lipochrome pig- 

 ments) or granular substance. 



3. Their location — In the scales, lower epidermis, dermis, or 

 all three. 



Considerable literature on the general histology of the shank 

 of birds is available. Of the earlier writers, Hanau (3) and 

 Jeffries (4) were the first to make exhaustive studies of the 

 dermal structures of birds. The work of the former on the 



"^ Papers from the Biological Laboratory of the Maine Agricultural 

 Experiment Station, No. 72. 



t Throughout the paper figures in parentheses refer to the literature 

 list at the end. 



