180 



THE PRINCIPLES OF BREEDING 



prises, but if well managed yields a proportionately greater 

 return. 



Principles of Breeding. — Breeding is the direction and con- 

 trol of tlie inherent life forces, heredity and variation, by means 

 of selection and mating. Its practice offers a means of regulat- 

 ing the progeny by control of the parentage. Improvement 

 should be the motive, it being something more than a mere mul- 

 tiplic<ation of numbers in the next generation. 



The forces involved are heredity, by means of which char- 

 acters are transmitted from generation to generation ; and varia- 

 tion, through the agency of which new characters are introduced. 

 The natural tendency in reproduction is toward variation, or the 

 production of unlike individuals, with heredity, acting as a 

 brake or check, opposed. The more intense the hereditary force, 

 the less marked the variation. The strength of the hereditary 

 force, so far as a specific character is concerned, is determined 

 by the extent to which that character is represented in the an- 

 cestry. The greater the number of individual ancestors there 

 are which possess it, and the greater the degree in which it is 

 possessed, the stronger the likelihood of its being transmitted. 



Heredity is, therefore, not a matter which involves only the 

 individuals mated, but all tliose ancestors whose characters and 

 hereditary forces the individuals in question possess. If the pre- 

 potency of all individuals in the ancestry were equal, the relative 

 influence of succeeding generations and individual ancestors 

 would be in accordance with Gralton's law as shown in the fol- 

 lowing: table : ^ 



* Davenport, " The Principles of Breeding. " 



