MORGAN AND GOODALE. INHERITANCE IN POULTRY 127 



of which must be present and one of which must be duplex in order to 

 bring about a complete suppression of the booting, the outcome approxi- 

 mates the observed ratios of booted to non-booted. 



By assuming that the factor which exerts its effect in either the duplex 

 or simplex condition is sex-linked, the results shown in Table II are 

 obtained. The distribution of the sexes is not given, because the numbers 

 available are inadequate for the solution of a problem as complex as the 

 present one. While the correspondence between theory and observation 

 in this case is close, an attempt to apply it to Davenport's data resulted 

 in only partial success. This may mean only that more or different fac- 

 tors are involved in the production of boot in Brahmas, Cochins and 

 Silkies than in Langshans, or that the factors causing the inhibition of 

 boot development in Plymouth Bocks are different from those of Tosa, 

 Minorca and other smooth-shanked birds used by Davenport. Among 

 possible factors concerned in boot production should be included those 

 general factors which affect feather growth, in the same way as barring 

 or other color factors control the color of the feathers of the boot as well 

 as those of the body. 



Down Colors. — The Langshan chick is black dorsally but yellowish 

 white beneath and has white wing tips. The white ventral area often 

 extends upwards, particularly on the head, so that in some eases in this 

 region only the crown and nape remain black. The white area of the 

 wing tips at the same time increases in size, so that the black dorsal 

 surface becomes reduced in amount. 



The Bock chick, however, though black dorsally except for the gray 

 occipital spot, is usually dark gray beneath, but very often there are 

 several light gray or white areas, which occasionally become more or less 

 confluent, and in extreme cases most of the ventral surface is white and 

 to a limited degree overlaps the Langshan type. 



In classifying the chicks, all were called "black," i. e., of Langshan 

 type, in which at most the breast region was partly pigmented. This 

 region in the Barred Bock chick is the last to lose pigment. All others 

 were classified as "barred". While this mode of treatment proved to be 

 inadequate for the entire solution of the inter-relations of these charac- 

 ters, it was found, first, that both types appear in F t , but that the 

 "blacks" are far more numerous than the "barreds" ; second, that "blacks" 

 ¥ 1 interbred or backmated throw some "barreds", but not in simple Men- 

 delian proportions. 



