116 MODES OF RESEARCH IN GENETICS 



produced by a further continuation of the same 

 method of breeding. If an apparent effect should 

 suddenly appear some time later than the tenth 

 generation, the case would need the most critical 

 scrutiny, to determine whether the observed 

 effect had really been due to the inbreeding, rather 

 than to some other unsuspected cause. 



The values of the Z's in Table I are maxima. 

 No particular coefficient of inbreeding can have a 

 higher value than that given in the table. It is 

 not possible, for example, so to breed any animal 



Fig. 1. Curves of inbreeding, showing (a) the limiting case of con- 

 tinued brother X sister breeding, wherein the successive coefficients of 

 inbreeding have the maximum values ; (b) continued parent X off- 

 spring mating ; (c) continued first-cousin X first-cousin mating where 

 the cousinship is double (C^ X C^), and (d) continued first-cousin 

 X first-cousin mating where the cousinship is single (C^ X CO- The 

 continued mating of uncle X niece gives the same curve as C^ X C^ 



