26 



INHERITANCE IN POULTRY. 



white legs, and toes that are usually but uot always meristically abnormal. 

 Wheu the hybrids are bred inter se we get varied combinations of char- 

 acteristics, as follows (D meaning dominant and R, recessive): 



Y \ 



Hernia. 



Absent (D) . 

 Absent . . . . 



Absent 



Present . . . . 

 Present . . . . 

 Absent ... 

 Absent . . . . 



Low (D) 



Low 



Low 



Low 



Low 



High 



High.... 



High I Absent 



High 



Low 



Low 



Low ... . 



Low 



I,ow .... 



Low 



High.... 

 High.... 

 High .... 

 High ... 



Low 



Low Absent 



Low 1 Absent 



Plumage. 



Normal (R)[ White (D) 



Normal....' Black and white. . 



Extra I White 



Normal .... I 



Extra j . 



Normal . . . . ^ White 



Normal ... ; Black and white. . 

 Extra : 



Present 



Absent 



Absent 



Absent 



Absent . 



Present 



Present 



Absent I Normal 



Absent ! Extra.. 



Present j Normal 



Present ! Extra. . 



Absent , Normal 



Normal 

 Extra.. 



Normal . . . 

 Normal . . . 



Extra 



Extra 



Normal. . . 

 Extra 



White 



Black and white. 



White 



Black and white 



White 



Black and white. 



Low. 



Present Normal. 



Low Present 



High j Absent. , 



High Absent. 



High Absent . 



High . Absent 



High [ Present 



High I Present 



High Present 



Extra 



Normal . . . i White 



Normal . . . . | Black and white. 



Extra i White 



Extra 1 Black and white. 



Normal . . . . ' White 



Normal. . . . i Black and white. 

 Extra. . . 



Actual No. 

 of cases. 



38 



CONCLUSIONS. 



In the series of crosses between the White Leghorn and Houdan, Mendeliau 

 results were obtained as in the first series. Dominance, however, is frequently 

 imperfect. The plumage color of the offspring of a pure homogametous white- 

 and-black and a white are rarely pure white. Likewise in the second hybrid 

 generation impure whites occur. Also, nostril-height exhibits imperfect 

 dominance of the narrow type. The muff, beard, and crest, though always 

 present in the first hybrid generation, are apparently always reduced. The 

 cerebral hernia, though recessive, affects the dominant normal skull. 



A heterosygous form results from hybridizing the single and V-shaped comb. 

 The cleft comb is a neomorph, of which more will be said in the sequel 

 (page 65). 



Polydactylism does not readily fall into the Mendelian formula. Hurst's 

 results, although suggestive, need support from other experiments. 



