CHAPTER VII. 



NOSTRIL-FORM. 



In my 1906 report I described in detail the form of the nostril in 

 poultry. Usually it is closed down to a narrow sUt, but in some races, as, 

 e. g., the Polish and Houdans, the closing flap of skin fails to develop and 

 the nostril remains wide open. This is apparently an embryonic condition. 

 Thus in Keibel and Abraham's (1900) Normaltafeln of the fowl it is stated 

 that the outer nasal opening, which is at first wide open, becomes closed with 

 epithelium at about the middle of the sixth day of development. The PoUsh 

 and Houdan fowl thus retain in the outer nasal opening an embryonic condi- 

 tion. The question is : How does this embryonic, open condition of the nostril 

 behave in heredity with reference to the more advanced narrow-sUt condition? 



The wide-nostriled races used were both the Polish and the Houdan. 

 The condition of the external nares is much the same in the two, but is 

 sHghtly more exaggerated in the Houdans than in the Pohsh. The open 

 nostril is often associated with a fold across the culmen, apparently due to 

 the upturning of the anterior end of the premaxillary process of the nasal 

 bone. Breeders of Houdans have sought to exaggerate the height of the 

 fold. In both races there is great variabihty in the degree of " openness" of 

 the nostril, and to indicate this I have adopted a scale of 10 grades (running 

 from 1, the narrowest, to 10, the widest) . To get some idea of this variabihty 

 let us consider the grade of nostril in some families of pure Houdans. 



Table 45 shows that the prevaiUng grade in the offspring of pure 

 Houdans is 9; that grades 8 and 10 are also extremely common; and that 

 lower grades, even down to 1, may occur, but these are much less common. 



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