BREEDING SYSTEMS 



247 



of individuals related for one generation, while in-and-in breeding 

 indicates those showing a longer period and closer degree of rela- 

 tionship. The two terms simply express a difference in the degree 

 of relationship of the mated birds. Three ways in which it is 

 possible to inbreed are: 



OFEMALB 



'/a 9 



Fig. 125. — Inbreeding chart showing distribution of inherited characters. The black 

 represents the blood lines of the male, and the white the blood lines of the female. The 

 solid black lines represent that a male has been chosen from the group from which they 

 start and the dotted lines that a female has been chosen. Inbreeding is traced through 

 four generations and the results are shown at the bottom of the chart. 



1. Breeding sire and daughter, which produces progeny with 

 one-fourth blood like the mother. 



2. Breeding son and mother, which gives progeny with three- 

 fourths blood like the mother. 



3. Breeding brother and sister, which produces progeny with 

 blood lines from both sire and dam in equal proportion. This 

 latter method is undesirable in general practice (Fig. 125). 



