ZOOLOGICAL POSITION AND STRUCTURE 17 



same (homonymous) spiral as those of the mouflon, 

 but the curves are somewhat differently arranged, 

 the tips of the horns, owing to a change in direc- 

 tion, forming the summits of downward, in place 

 of upward, spirals (compare pi. i. fig. i with 

 pi. xi. fig. 2). This change in the direction of 

 the tips of the spirals, which is repeated among the 

 sheep in the North African arui {Antmotragus 

 lervia) and the Tibetan bharal {Pseudots nahura), 

 and among the goats in Pallas's tur {Capra cylin- 

 dricornis) of the Caucasus, is technically known as 

 a mathematical perversion, and causes the horns 

 to bend backwards behind the neck, instead of 

 coming forwards by the sides of the face. 



From this it will be evident that all sheep, 

 both wild and tame, have horns of the homonymous 

 type. 



Reverting to the consideration of the structural 

 differences between sheep and oxen, it remains to 

 point out that whereas all the latter are long-tailed 

 animals, every species of wild sheep, save the 

 aberrant African arui, has a short tail, only slightly 

 exceeding in length that of an ordinary deer. A 

 similar or nearly similar condition obtains in several 

 of the more primitive breeds of domesticated sheep, 

 although, on the other hand, in the majority of such 

 breeds the tail becomes more or less markedly 

 elongated, or undergoes abnormal development in 

 other ways ; all such departures from the wild type 



