18 POULTRY BREEDING AND MANAGEMENT 



and varieties separate; and crossing was no doubt freely 

 resorted to. Crossing adds to size and vigor, produces varia- 

 tions and abnormalities, restores lost or latent characteris- 

 tics and increases fertility. Our present types and races 

 of chickens were undoubtedly evolved in part from cross- 

 ing. 



Summary. It is known, therefore, that all breed im- 

 provement is founded on variation. It is further known 

 that variation may be induced by certain other conditions 

 or factors. A change from one climate to another is a fruit- 

 ful source of variation. This is true of plants as well as 

 animals. A change of climate often gives increased vigor 

 and fertility. Changes in climate and changes in food have 

 undoubtedly had a great deal to do with the evolution of 

 the fowl. Transplanted to a cold climate, we find the jungle 

 type of three pounds has evolved into the twelve-pound fowl, 

 because the fleshy fat fowl was better fitted to withstand 

 the cold. On the contrary, the southern climates are not 

 favorable to the heavy fowl, with heavy feathering and 

 abundant fat, and as a consequence there was gradually 

 evolved the Leghorn and fowls of that type. 



Again, abundant food that was assured with domestica- 

 tion, undoubtedly exercised a potent influence in determin- 

 ing the size and characteristics of the fowl. Plenty of food 

 tends to increase the size ; scanty nutrition results in small 

 races. Good food increases fecundity. 



Crossing, however, is probably the most powerful means 

 of variation. Crossing different breeds or varieties opens 

 the door to further improvement, and to other breeds. 



