12 BREEDING OF 



GENERAL PRINCIPLES. 



THERE are certain biological laws which relate to Re- 

 production, to which all animals are subject. Many of 

 those laws have only been formulated within the past 

 half century; in fact, to the influence of Charles Darwin 

 more than any other man, or perhaps any ten men, is 

 due the formulating of reproductive laws and the 

 grouping of facts relating to them. 



The two underlying principles each of which is op- 

 posed to the other and by which all breeders are 

 guided, are Heredity and Variation, 



HEREDITY. 



WHEREVER we look in the field of Natural History, 

 the one fact that stands out more prominent than any 

 other is the strong tendency for like to beget like; yet 

 if this were an invariable rule there could be no change 

 in types of animals, and there could be no advance- 

 ment in breeding. Again, unless the principle of 

 heredity was exceedingly strong, there would be no 

 permanent fixity of any improvement which might be 

 produced by any scientific breeder. But under the 

 strong influence of the law of heredity any chance 

 improvement which may occur in any breed of animals, 

 can almost certainly be reproduced in future individ- 

 uals that may be born as a result of pairing the animal 

 in which the improvement has appeared, with another 

 of the same species. The failure to reproduce this im- 



