36 THE SHEEP AND ITS COUSINS 



my volumes on The Ox and Its Kindred and The 

 Horse and Its Relatives were strictly adhered to, 

 this course would have to be adopted. Since, how- 

 ever, it seems inadvisable to interfere more than is 

 absolutely essential with generally accepted systems 

 of classification, the more typical sheep are here 

 separated from the goats {Copra) as Ovis, while the 

 aberrant arui and bharal are assigned to genera by 

 themselves. 



As the various modifications produced in sheep 

 by domestication are more or less fully described in 

 the sequel, they need not be referred to in detail in 

 this place. Many at least of these modifications 

 would appear to be the result of accumulated slight 

 changes produced by the influence of climate, soil, 

 food, &c. The fat-rumped character, for instance, 

 seems to be intimately connected with a dry 

 climate and saline soil, accompanied by aromatic 

 and saline plants as food ; for when removed from 

 such surroundings fat-rumped sheep tend to lose 

 in greater or less degree the feature from which 

 they derive their name. 



On the other hand, there is evidence that breeds 

 may occasionally be produced by sudden mutations, 

 as is exemplified by a well-known case quoted by 

 Darwin,^ who wrote as follows : — 



"Thus, in 1791, a ram-lamb was born in Massa- 



• Animals and Plants under Domestication, vol. i. p. 104, 2nd, 

 ed., London, 1885. 



