182 THE PRINCIPLES OF BREEDING 



the first five or six generations, is in proportion to the merit of 

 the individuals recorded. 



Prepotency is the breeding power of a stallion or mare, 

 measured by the degree witli which their likeness is transmitted 

 to their get. It should be distinguished from fecundity, which 

 is the reproductive power, measured by the regularity with 

 which progeny are begotten by the sire or produced by the dam. 

 Prepotency is determined by the uniformity of the ancestry, 

 which, in turn, is most intensively insured by line and inbreed- 

 ing. There is, furthermore, a difference in the prepotency of 

 individuals similarly bred. 



Fecundity is marked in certain families, showing its hered- 

 itary and transmissible nature, and is frequently associated with 

 longevity. The individual element is also a factor in fecundity. 



Line breeding is the mating of tsvo individuals having a 

 common ancestor but a few generations removed. It is prac- 

 ticed for the purpose of intensifying tlie hereditaiy force derived 

 from certain individuals. It is a compromise on inbreeding. 



Inbreeding is the mating of brother and sister, sire and 

 daughter, son and dam, thus eliminating all but the blood from 

 certain individuals. It is rarely practiced by horse breeders. 



Cross-breeding is the mating of pure-bred individuals but 

 of different breeds. Indiscriminate cross-breeding is to be con- 

 demned, but intelligently conducted it is justifiable for certain 

 purposes, as in the production of hunters in this country. Cross- 

 breeding has the effect of producing variation. The more radical 

 the cross the more extreme and uncertain the variation. It is 

 resorted to for several purposes : (1) Either to restore vigor and 

 fecundity to stock that has been bred too long in one line or 

 under the same environment; (2) to graft on one breed some 

 desirable characters of another; (3) to blend, permanently, the 

 breed characters of two breeds ; or simply to combine these char- 

 acters in the progeny of one generation. To this end it may 

 consist either of making a single infusion of the blood of an 

 alien breed, as the Thoroughbred cross on the Standardbred ; of 

 making cross-breds the basis of a new breed, as in the foundation 

 of the French Coach from the demi sang ; or continuing to cross 

 breed without interbreeding the cross breeds, as in the production 



