484 



The Journal of Heredity 



or the repulsion between two factors 

 resulting in what is known as sex- 

 limited inheritance. 



An explanation of what constitutes 

 dominance or recessiveness is unneces- 

 sary and is not offered in this paper. It 

 is only desired to show in tabular form 

 the dominance and recessiveness of 

 many of the common characters of 

 poultry as they have been worked out. 

 For this purpose it is impossible to do 

 better than to use intact the table 

 given by Dr. P. B. Hadley in the 1915 

 American Poultry Year Book. 



blues when bred together give blacks, 

 splashed whites and blues in the usual 

 mcndelian proportion. Here the black 

 color and the splashed white seem to be 

 the mcndelian characters, neither of 

 which ]3roves to be dominant but the two 

 exist side by side in the hybrid in a 

 minute mosaic which causes the blue 

 color. The blue individual is therefore 

 always heterozygous or "inongrel." 



In addition to the characters tab- 

 ulated, recent studies ^\dth the "bare- 

 neck" breed of poultry support the 

 view that the nature of the factor which 



Table Showing the Mode of Inherit.vnce of Some of the Common Characters of Poultry 

 Dominant Recessive Remarks 



Dominant white (Leghorn) Black, red, buff Almost complete dominance 



Black, red, buff Recessive white (Minorca) Almost complete dominance 



Black' (Hamburg, Minorca) Red, buff (Wyandotte) Almost complete dominance 



Barred plumage-pattern Recessive white, black self -color. .Sex-limited inheritance 



Game pattern (Leghorn) Recessive white (Minorca) Sex-limited inheritance 



Black self-color (Minorca) Hackle-lacing (Brahma) Imperfect dominance 



Plain feathering Silky feathering Complete dominance 



Frizzle feathering Normal repent feathering Complete dominance 



Rose or pea comb Single comb Complete dominance 



Single comb Comblessness (Breda) Complete dominance 



Crest (Silky) No crest Imperfect dominance 



Normal head Cerebral hernia (Polish) Imperfect dominance 



Rumplessness Normal uropygium Imperfect dominance 



Extra toes Normal foot Imperfect dominance 



Joining of toes Normal foot Imperfect dominance 



Silky pigmentation Normal mesoderm color Imperfect dominance* 



Yellow skin color White skin color Complete dominance 



Yellow shank color Light shank color Complete dominance 



Dark shank color Light shank color Complete dominance 



Black iris color Brown, red, pearl iris Complete dominance 



Red ear-lobe White ear-lobe Imperfect dominance 



Feathered shanks Clean shanks Imperfect dominance 



Plain heel Vulture hock (Silky) Imperfect dominance 



Booting (Silky) No booting Imperfect dominance 



Beard (Houdan) No l)eard Almost complete dominance 



Long tail (Japanese) Normal tail Imperfect dominance 



Rapid feathering Slow feathering Almost complete dominance 



Broodiness (Silky) Non-broodiness Almost complete dominance 



* Sex-limited in Brtnvn Leghorn and Silky crosses. 



It will be noted from this table that 

 in only a few cases is dominance listed 

 as complete. There is a variation all 

 the way from complete dominance to a 

 very weak dominance and to explain 

 this variation it has been necessary to 

 fall back u]jon the idea of prepotency. 

 It might also be well to call attention 

 here to the case of the blue color of the 

 Andalusian where neither of a pair of 

 characters shows dominance over the 

 other. The Black Andalusian and the 

 Sjjlashed White Andalusian bred to- 

 gether give all blue offspring. These 



]jrcvcnts feather growth on the neck is 

 dominant. 



SEX-LLMITI':!) INHERIT.\XCE 



Certain of the characters of domestic 

 poviltry are inherited in a manner 

 known as sex-limited. We are accus- 

 tomed to observing the ustial limitation 

 of certain secondary sexual characters to 

 their respective sexes, such as the spur 

 and long sickle feathers of the cock, 

 but it has remained for experimental 

 breeding to point out that certain other 

 characters arc also sex-limited. Per- 



