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INBREEDING AND OUTBREEDING 



Two individuals may have the same Coefficients of In- 

 breeding when considered for any given number of gen- 

 erations, but differ greatly in germinal constitution. This 

 is due to the fact that the two lines brought together in 

 the immediate production of any individual may or may 

 not be related. For example, a closely inbred animal of 

 one breed may be mated to another closely inbred animal 



Generations 



Fio. 22. Curves of inbreeding showing (a) the limiting case of continued brother 

 X sister breeding, wherein the successive coefficients of inbreeding have the maximum 

 values; (6) continued parent offspring mating; (c) continued first cousin X first cousin 

 mating where the cousinship is double (C* XC 1 ), and (d) continued first cousin X first 

 cousin mating where the cousinship is single (C 1 XC 1 ). The continued mating of uncle X 

 niece gives the same curve as C 1 X C 1 . (After Pearl.) 



of an entirely different breed. The two lines of descent 

 would then be totally unrelated as far as the known pedi- 

 grees are concerned, but the resulting individual would 

 have a high Coefficient of Inbreeding, due to the concen- 

 tration of ancestry separately in the two ancestral lines. 

 To give some measure of the inter-relation of the lines of 

 descent, Pearl has devised the Coefficient of Relationship, 

 K, which is essentially the per cent, of the individuals in 



