Chap. III. SHEEP : THEIE VAKIATION. 93 



this bull greatly improved his race. We have also reason to 

 believe that selection, carried on so far unconsciously that there 

 was at no one time any distinct intention to improve or change 

 the breed, has in the course of time modified most of our 

 cattle ; for by this process, aided by more abundant food, all the 

 lowland British breeds have increased greatly in size and in early 

 maturity since the reign of Henry VII. 72 It should never be 

 forgotten that many animals have to be annually slaughtered ; 

 so that each owDer must determine which shall be killed and 

 which preserved for breeding. In every district, as Youatt has 

 remarked, there is a prejudice in favour of the native breed ; so 

 that animals possessing qualities, whatever they may be, which 

 are most valued in each district, will be oftenest preserved ; 

 and this unmethodical selection assuredly will in the long run 

 affect the character of the whole breed. But it may be asked, 

 can this rude kind of selection have been practised by barba- 

 rians such as those of southern Africa ? In a future chapter on 

 Selection we shall see that this has certainly occurred to some 

 extent. Therefore, looking to the origin of the many breeds of 

 cattle which formerly inhabited the several districts of Britain, 

 I conclude that, although slight differences in the nature of 

 the climate, food, &c, as well as changed habits of life, aided 

 by correlation of growth, and the occasional appearance from 

 unknown causes of considerable deviations of structure, have all 

 probably played their parts ; yet that the occasional preserva- 

 tion in each district of those individual animals which were 

 most valued by each owner has perhaps been even more effec- 

 tive in the production of the several British breeds.' As soon 

 as two or more breeds had once been formed in any district, or 

 when new breeds descended from distinct species were intro- 

 duced, their crossing, especially if aided by some selection, will 

 have multiplied the number and modified the characters of the 

 older breeds. 



Sheep. 



I shall treat this subject briefly. Most authors look at our 



domestic sheep as descended from several distinct species ; but 



how many still exist is doubtful. Mr. Blyth believes that there 



n Youatt on Cattle, p. 116. Lord Spencer has written on this same subject. 



