46 



PRACTICAL POULTRY PRODUCTION 



Variation. By using the same example as given above 

 under heredity we may find in the offspring of the mating 

 of White Plymouth Rocks 'one or more birds that are supe- 

 rior to their parents in type, size, or production. On the 

 other hand some of the offspring may be inferior to the 

 parents in these qualities. This difference is called varia- 

 tion. It is by taking advantage of this law of breeding and 

 selecting the birds which show improvement in appearance, 

 performance, and size over the parent stock that progress 

 is made. 



Figure 46. — This White Leghorn hen pos- Figure 47 — A White Leghorn hen of poor 



sesses the standard requirements of standard qualities, which produced over 



her breed and produced over 200 eggs 200 eggs in a year, 

 in one year. 



Sports, or mutations. By this term is meant the occur- 

 rence of individuals that are characterized by being radically 

 different in type or color from their own ancestors. An 

 example of a "sport" can be cited in the case of the White 

 Minorca which is claimed to have been produced from a 

 mating of Black Minorcas. 



Reversion, or atavism, refers to the cropping out or 

 appearance of characters in the offspring which are not found 

 in the immediate parents but which were present in some of 



