ZOOLOGICAL POSITION AND STRUCTURE 15 



The Ammon type is, however, by no means the 

 only one found in sheep, for in the African long- 

 legged breeds, as shown in the text-figures in 

 chapter xi. and in pi. xvi. fig. i, the horns are, 

 so to speak, pulled out or stretched, so as to 

 lose almost completely the snail-like curve, and to 

 be twisted on their own axis. In this breed the 

 direction of the horns is almost immediately out- 

 wards, but in the Wallachian sheep, or zackel- 

 sheep (pi. ix. fig. i), the horns are directed 

 obliquely upwards and outwards, and the twisting 

 on their own axis in screw-style is still more 

 marked. In all these cases the spiral is of the 

 homonymous type, that is to say, the right horn 

 forms a right-handed spiral.^ We thus have a 

 complete gradation from what Mr. Theodore Cook ^ 

 terms the curved type, as exemplified by ordinary 

 sheep, to the twisted type, as shown in the 

 markhor among goats and in the bushbuck and 

 kudu among antelopes. 



The coexistence of the two types in sheep is 

 remarkably well exemplified by an ancient Egyptian 

 fresco (1449- 1 423 B.C.) reproduced in the accom- 

 panying illustration,* which is evidently a composite 



• Mr. Cook, Spirals in Nature, regarded the horns of the Wal- 

 lachian sheep as of the heteronymous type. 



' Loc. cit. 



' This figure was tentatively regarded by Dr. A. E. Shipley, 

 Country Life, March 23, 1912, p. 426, as that of a four-horned 

 ram. 



