PRINCIPLES OF POULTRY BREEDING 



81 



and preferably from other sections of the country, to im- 

 prove vigor. 



Tlie two alternatives are crossing and outcrossing. The 

 theoretical objection to crossing is that it disturbs blood 

 lines, and the influence of ancestry is lost. In other wqrds, 

 while it may " improve the breed it spoils the blood. " 

 While crossing often results in improved strains that excel 

 their parents, causing a tendency upward, it is also true that 



THE RECESSIVE COLOR BARRING 



Barred Rock and White Leghorn Cross. D621 laid 275 eggs; D. 622 laid 

 272 eggs in a year. (Oregon Station.) 



crossing sometimes reverses the engine of evolution and 

 throws backward. This usually happens when it is con- 

 tinued beyond the first generation. Crossing cross-breds 

 with cross-breds will start the engine going backward; in 

 other words, reversion will happen, and the result is likely 

 t6 be mongrels, or even a type resembling in some charac- 

 teristics the wild ancestor. Indiscriminate crossing will 

 lead to degeneracy just as surely as will indiscriminate in- 

 breeding. The first cross will give vigor, as much, probably, 



