BREEDING 



127 



Cross-breeding.— Two kinds of cross-breeding are practised. 

 With the first, which is used in endeavoring to find a new 

 combination of characters or qualities and thus form a new 

 breed, individuals of different Ipreeds whose blended characters 

 it is hoped will approach the combination sought are mated 

 and selected progeny of the cross are used as breeders for 

 further operations. An illustration of this is found in the 

 formation of the American breeds. 



Fig. 63 



A cross-bred hen carrjring three-eighths Barred Plymouth Rock blood 

 and five-eighths Single Comb White Leghorn. Egg record, 291 in twelve 

 months. (Courtesy of Oregon Experiment Station.) 



With the second the two breeds are kept in their purity, 

 and the progeny, which always represent a first cross, are 

 never used for breeding purposes. Thus it is said that for 

 producing Philadelphia capons a cross much employed is 

 that of the Light Brahma and White Plymouth Rock. 

 The offspring always carry half their blood from each breed. 

 For producing market ducks a cross much used is that of the 

 Pekjn and Aylesbury. In such breeding it should always 



