22 



INHERITANCE IN POULTRY. 



judge this equality to indicate a difference of color in sex ; or else the pig- 

 mented individuals are heterozygotes. Possibly the females are the hetero- 

 zygous forms the males homozygous. 



2. COLOR OF UPPER MANDIBLE. This assumes its final condition so late in 

 life that definite statistics will not be given now. 



First hybrid generation. A few young are recorded as showing yellow. 

 The rest are white ; this is probably the young condition of the light horn 

 of the adult Houdan. I/ight horn seems dominant. 



Second hybrid generation. A few cases of black mandible are recorded, 

 even in the young, where pigment is less developed. 



First hybrid (87) crossed with white Leghorn. All older chicks have white 

 mandibles ; there are no blacks. 



3. NOSTRILS. First hybrid generation. Of 25 individuals, all but one have a 

 nostril of one-half width or less thus approaching the white Leghorn type. 

 The exceptional individual (No. 386 9 ) has a typical high nostril and is 

 peculiar in respect to comb also. Only one individual is recorded as having 

 as narrow a nostril as the Minorca. 



Second hybrid generation. Forty-nine individuals give : 



On the assumption that " narrow and intermediate " includes pure- narrow 

 and heterozygous individuals, while " high " includes recessive, pure-high 

 individuals, we should expect 75 per cent and 25 per cent in the two classes 

 respectively only an approximate agreement with the actual. 



First hybrid {No. 87$} crossed with white Leghorn (//$). The father 

 has a "one-fourth" nostril; the mother, of course, a typical "narrow" 

 one. Of 24 individuals 12 are recorded as narrow; 12 as intermediate of 

 some grade. This gives the ratio 1:1, which we expect, assuming the inter- 

 mediate nostril to be the heterozygous type ; the narrow, the pure type. 



4. COMB. First hybrid generation. Of 41 individuals 40 have the Y-shaped 

 comb in some form (fig. 17). This comb resembles that of the Minorca 

 X Polish hybrid. There is no case of a single comb in this generation, but 

 there are two cases in which the posterior end of the comb is merely much 

 thickened. On the whole the present series of cleft combs differs from the 

 former in that a smaller proportion of the comb is split no cases of wholly 

 split or cup combs occur, although in one important case (87 $ ) two-thirds 



