620 PRACTICAL PROBLEMS 



RELATIVE EFFECT OF OUTBREEDING AND OF INBREEDING 



From this we see that both systems produce the same mean, 

 but that inbreeding produces the wider extremes (3 and i). 

 Hence the greatest range of possibilities lies with inbreeding, so 

 far as immediate parentage alone is concerned, and the advantage 

 is of course still greater in the ancestry farther back. 



Again, the table shows what will happen on the average under 

 the law of regression, but in exceptional cases the law of pro- 

 gression will apply, from which we see that the advantage for 

 inbreeding is still greater ; in other words, it is by inbreeding 

 that the highest and the lowest attainable results can be pro- 

 duced, and this is because no other system can produce so high 

 (or low) a mid-parent, or in the end so " pure " an ancestry. All 

 of this indicates a principle that is abundantly powerful for 

 intensifying good characters or for breeding out evil ones. The 

 fact that it is thus powerful argues against its use with any but 

 superior individuals. Furthermore, inbreeding is a supreme test 

 of excellence, and if a family line or an individual endures it, its 

 characters are above reproach. 



Not all inbred individuals inferior to the cross-bred, even in 

 species especially sensitive to inbreeding. One of Darwin's most 

 extensive series of experiments was carried on with the common 



