86 INHERITANCE IN POULTRY. 



Various authors refer to the imperfection of the dominant or recessive 

 characteristic in the hybrid. 'Bateson and Saunders (1902, p. 23) say : V 



Although the offspring resulting from a cross between any two of the forms (of Datura) 

 employed is usually indistinguishable from the type which is dominant as regards the 

 particular character crossed, yet in other casas the intensity of a dominant character may 

 be more or less diminished either in particular individuals or in particular parts of one 

 individual. 



i Hurst (1905, pp. 145-154) records many cases of imperfect dominance in 

 poultry and estimates the incomplete dominants to be twice as numerous as 

 the complete dominants. 



./ DEPENDENCE OF DOMINANCE ON THE RACES CROSSED. 



Is one of a pair of allelomorphs that shows itself dominant when varieties 

 A and B are crossed likewise dominant when any other varieties, M and IV, 

 are crossed, or is the relative potency of the allelomorphs dependent upon 

 the varieties in which they happen to reside ? 



Data for an answer to this question are to be found in the experiments where 

 the same pair of allelomorphs were crossed , using different varieties. We may 

 except from this list the Minorca x Polish and the Leghorn x Houdau crosses, 

 as the races involved are very closely related. The following allelomorphs, 

 remain for consideration : 



(1) Crest vs. crestlessness. (6) Extra vs. normal toes. 



(2) Silkiness vs. non-silkiness. (7) Black vs. white skin. 



(3) Rumplessness vs. tail. (8) Black vs. yellow beak. 



(4) Vulture hock vs. plain hock. (9) White vs. dark plumage. 



(5) Boot vs. clean foot. 



Crest. This is dominant when Polish or Houdan is crossed with the 

 Mediterranean breeds and when the Silky is crossed with the Frizzle or with 

 the Jungle fowl. Crest is uniformly dominant over crestlessness, no matter 

 which of these races are used. 



Silkiness is recessive to non-silkiness when crossed with Frizzle or the 

 Jungle fowl. Non-silkiness is probably always dominant. 



Rumplessness in a Game fowl was recessive to the tailed condition of Leg- 

 horn, Cochin, Frizzle, and Nankin. The tailed condition seems always to 

 dominate. 



Vulture hock is recessive when an Asiatic race is crossed with any Med- 

 iterranean breed or a Game, and probably, in general, plain hock dominates. 



Booting is dominant when the booted form is the mother, no matter what 

 the race. Booting is much reduced and sometimes altogether absent in the 

 first generation of hybrids when it is derived from the father. Inheritance 

 of booting is independent of race but not of sex (p. 38). 



Extra toe seems not to Mendelize. The excess of extra toes in the first 

 hybrid generation holds for all the races crossed and is probably independent 

 of race. 



