216 INBEEEDING AND OUTBEEEDING 



formity and the concentration of desired qualities. So 

 valuable have been the results, particularly with animals, 

 that it has often been continued even though concentra- 

 tion of characters which made for lessened constitutional 

 vigor and fertility accompanied the accumulation of de- 

 sirable features, for the good outweighed the evil. To 

 overcome anticipated calamities, animal breeders have 

 from time to time introduced fresh stock. In doing this 

 they certainly were wise, since a rather high probability 

 always exists that such a procedure will introduce the 

 dominant complements of the detrimental characters. 

 But even granting the good sense at the base of both prac- 

 tices, it may be doubted whether inbreeding and cross- 

 breeding have been used in the best possible manner as 

 means of improvement. There are precise uses to which 

 each may be put which hitherto have not been considered. 

 Experiments with maize show that undesirable quali- 

 ties are brought to light by self-fertilization which either 

 eliminate themselves or can be rejected by selection. The 

 final result is a number of distinct types which are con- 

 stant and uniform and able to persist indefinitely. They 

 have gone through a process of purification such that only 

 those individuals which possess much of the best that was 

 in the variety at the beginning can survive. Although 

 these resultant, purified types have little value in them- 

 selves, they have possibilities. The characters which they 

 have can now be estimated more nearly at their true 

 worth. By crossing, the best qualities which have been 

 distributed to the several inbred strains can be gath- 

 ered together again and a new variety re-created. Size, 

 vigor and fertility can be fully restored with the advan- 



