14 THE SHEEP AND ITS COUSINS 



mouflon type, as it may be otherwise called — the 

 right horn forms a right-handed spiral and the left 

 horn a left-handed spiral ; this condition being 

 called homonymous, as opposed to heteronymous, 

 in which the right horn forms a left-handed spiral, 

 and vice versa. This heteronymous condition is 

 displayed by antelopes and wild goats (especially 

 the Himalayan markhor) ; but, curiously enough, 

 tame goats, with the exception of the Circassian 

 breed, have horns with the spiral running in the 

 same direction as in sheep, that is to say, they are 

 of the homonymous type.^ It may be added that 

 there are certain extinct European antelopes, con- 

 stituting the genus O'ioceros, in which the spiral is 

 homonymous, as in sheep.^ 



As the subject of spirals is a somewhat difficult 

 one, it may be well to mention that an ordinary 

 screw or a corkscrew represents a right-handed 

 spiral. In following the ridge on such a right- 

 handed spiral we pass continuously to the left ; 

 and this has led some Continental writers * to 

 describe the Ammon or mouflon type of horn as a 

 left-handed spiral, which is incorrect. 



1 See G. Wherry, " On the Direction of the Spiral in the Horns 

 of Ruminants," British Medical Journal, September 27, 1902 ; T. A. 

 Cook, Spirals in Nature and Art, London, 1903, p. 77, and "The 

 Spirals of Horns," Field, July 27, 1912. 



» See C. Gaillard, " Le Belier de Mend^s," Bull. Soc. Anthrop. 

 Lyon, 1 901, p. 24. 



• Gaillard, op. cit., and Fitzinger, Sitzber. Ak. Wiss. Wien, vol. 

 xxxviii. p. 156, 1859. 



