PRINCIPLES OF POULTRY BREEDING 77 



stand this strain on her reproductive organs, her vitality 

 must not have been impaired by any system of breeding. 

 To demand production of that intensity from a strain of 

 fowls that have been bred and inbred for generations for 

 any special point is to demand the impossible. It is not 

 here claimed that standard-bred fowls or show birds are 

 necessarily poor layers. It is not impossible for the breeder 

 to breed show birds and at the same time maintain the vital- 

 ity necessary for the high production, but close breeding 

 for either fancy points or utility points will not insure 

 good layers, any more than the same kind of breeding with 

 mongrels will produce good layers. 



(4) New breeds and varieties are produced by crossing. 

 Most of our modern breeds are the result of cross breed- 

 ing. Crossing induces variation, and it is in taking ad- 

 vantage of these variations that new breeds and varieties 

 arise. Some crosses or hybrids possessing desired charac- 

 teristics breed true, and the type at once becomes fixed. On 

 the other hand, the great majority will not breed true, and 

 years of careful selection will be necessary to fix the type. 

 The Plymouth Rock, Wyandotte, Rhode Island Red, and 

 other breeds are all the result of crossing. The Orpington, 

 of more recent origin, resulted from crossing many breeds, 

 and William Cook, the originator, said that he got "so many 

 more eggs than he did when the breeds were pure that it 

 gave him a new idea." 



Jordan and Kellogg, in "Evolution and Animal Life," 

 say, ' ' Often as much progress can be made in a single suc- 

 cessful cross or hybridization as in a dozen or even a hun- 

 dred generations of pure selection. ' ' 



The Primus berry was produced by Luther Burbank with 

 a cross between the Siberian raspberry and the California 

 Dewberry. Its fruit excells either parent in abundance 

 and size, and ripens before the two parents begin to bloom. 



