Chap. XV. OF UNIFORMITY OF CHARACTER. 63 



separated his animals. The killing of inferior animals in 

 each generation comes to the same thing as their separation. 

 In savage and semi-civilised countries, where the inhabitants 

 have not the means of separating their animals, more than 

 a single breed of the same species rarely or never exists. In 

 former times, even in the United states, there were no distinct 

 races of sheep, for all had been mingled together. 1 The cele- 

 brated agriculturist Marshall 2 remarks that " sheep that 

 " are kept within fences, as well as shepherded flocks in open 

 " countries, have generally a similarity, if not a uniformity, 

 "of character in the individuals of each flock;" for they 

 breed freely together, and are prevented from crossing with 

 other kinds; whereas in the unenclosed parts of England 

 the unshepherded sheep, even of the same flock, are far from 

 true or uniform, owing to various breeds having mingled 

 and crossed. We have seen that the half-wild cattle in 

 each of the several British parks are nearly uniform in cha- 

 racter ; but in the different parks, from not having mingled 

 and crossed during many generations, they differ to a 

 certain small extent. 



We cannot doubt that the extraordinary number of varieties 

 and sub-varieties of the pigeon, amounting to at least one 

 hundred and fifty, is partly due to their remaining, dif- 

 ferently from other domesticated birds, paired for life once 

 matched. On the other hand, breeds of cats imported into 

 this country soon disappear, for their nocturnal and rambling 

 habits render it hardly possible to prevent free crossing. 

 Eengger 3 gives an interesting case with respect to the cat 

 in Paraguay : in all the distant parts of the kingdom it has 

 assumed, apparently from the effects of the climate, a peculiar 

 character, but near the capital this change has been pre- 

 vented, owing, as he asserts, to the native animal frequently 

 crossing with cats imported from Europe. In all cases like 

 the foregoing, the effects of an occasional cross will be aug- 

 mented by the increased vigour and fertility of the crossed 

 offspring, of which fact evidence will hereafter be given ; for 



1 'Communications to the Board of England,' 1808, p. 200. 

 Agriculture,' vol. i. p. 367. 3 ' S'augethiere von Paraguay. 



2 ' Review of Reports, North of 1830, s. 212. 



