Bulletin 160 



SOME DATA ON THE INHERITANCE OF 

 HORNS IN SHEEP 



By T. R. Arkell 



For many years scientists and practical breeders have devoted 

 much time to solving the phenomenon that surrounds the inheri- 

 tance of horns in sheep. Horns offer a fertile field for experi- 

 mental breeding investigations, since they represent a patent 

 character that can be readily distinguished in the soma and the 

 degree of potency in which they may appear in different crosses 

 can be accurately ascertained by actual measurement. Horns 

 in sheep, however, do not have the simple manner of inheritance 

 that do horns in cattle. The production of horn in the former 

 is influenced and controlled most strongly by sex, exhibiting a 

 markedly different condition in each sex, whereas in the latter 

 there occurs in both male and female the simple dominance of 

 an inhibitor to horn growth. 



Attention was called by Darwin* in 1871 to the fact that, when 

 a cross is made between pure horned and hornless sheep — it 

 matters not which sex bears the horns — the male offspring event- 

 ually develops horns of some kind but the females are hornless. 

 Wood t (1905)published a note which, based on actual breeding 

 tests, corroborated Darwin's findings. Wood carried his inves- 

 tigations further, breeding the Fi generation inter se and dis- 

 covered that of the F 2 males approximate^ seventy-five per 

 cent, were horned and twenty- five per cent, polled while the 

 opposite condition obtained in the females; namely, twenty-five 

 per cent, horned and seventy-five per cent, polled. This percent- 

 age of horned and hornless individuals coincided with Mendelian 

 expectation, showing that the interpretation of this phenomenon 

 according to Mendel's theory, was a just and accurate one. 

 Wood obtained his results from reciprocal crosses between Dorset 

 Horn, a breed having both males and females horned, and Suffolk 

 Down, of which both sexes are hornless. Darwin's data were 

 gotten from sources of a similar nature, except that for the horned 

 breed, Lonk sheep were used and for the hornless, Leicesters 

 and Shropshire Downs. 



The data of Darwin and Wood, however, do not cover the 

 entire scope of horns in sheep; for sheep, according to the condi- 

 tion of horns they bear, may be divided into three distinct 

 categories: Breeds with both males and females heavily horned 



* Darwin, Charles, "The Descent of Man and Selection in Relation to Sex," New York, Appleton. 



t Wood, T. B., " Note on the Inheritance of Horns and Face Color in Sheep," Jour. Agric. Sci., 36'}, 365, pi. IV. 



