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Ch. XXXVI.] DIFFEEENT EACES OF CATTLE HEED APAET. 311 



varieties. If we prefer the latter, we are compelled to ques- 

 tion tlie reality of the distinctness of all other suj)posed 

 species which differ no more than the parents of such pro- 

 lific hybrids ; for although we may not be enabled immedi- 

 ately to procure, in all such instances, a fruitful offspring, 

 yet experiments show, that sometimes after repeated failures, 

 the union of two recognised species may at last, under very 

 favourable circumstances, give birth to a fertile progeny. 



Two kinds of pheasant, our common species, Phasianus 

 colchicnSy and P. torquatuSy breed together, and the hybrids 

 are perfectly fertile.^ The two pimpernels, as before stated 

 (p. 308), cannot be crossed. 



r 



lency of different races of domestic cattle and sheer) to herd 



fc) 



more 



more 



apart. — Alt! 



jackal have been crossed with the dog, and this mixture is sup- 

 posed to have contributed somewhat to the great diversity 

 of our artificial breeds, yet these same wolves and the jackal 

 keep distinct in a wild state, 

 aboriginal races or subspecies of European wild cattle, which 

 kept distinct in prehistoric times, have now been blended 

 and confounded together, and even the humped cattle of 

 India have been crossed with our domestic varieties and have 

 produced fertile offspring. Two species of wild pig, as before 

 stated, the European Sus Scrofa and the 8us Indica, have also 

 been confounded together in some of our domestic races. 

 Yet there is every reason to believe that such mixtures would 

 not have occurred in a state of nature. This may be ex- 

 plained simply by the preference which animals exhibit to 

 unite with others of the same race rather than with those 

 which differ considerably from them. 



In Paraguay the horses have much freedom, and those of 

 the native race of the same colour and size prefer associating 

 together rather than with other imported horses. Three 

 distinct sub-races of the horse in Circassia, whilst living nearly 

 a free life, refrain almost 



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been observed in 



It has 



a 



Norfoll 



district stocked with heavy Lincoln- 

 sheep, that both kinds will, when 



Origin of Species, 4tli edition, p. 300. 



