8 Breeding Plants and Animals. 



age, the majority being nearly at the average, and a 

 few being far above the average. 



2. Breeding is ordinarily done mainly by selecting 

 the small per cent, which are above the average, and 

 improvements come surely though slowly. 



3. Among the small percentage of best individuals 

 variation exists as to their prepotency or breeding 

 power ; some being poor, the many nearly average, and 

 a few excelling; these latter being a very small per- 

 centage of the entire number in the class, breed or 

 variety. 



4. By choosing for parents those superior indi- 

 viduals having especially potent blood, the breed or 

 variety is rapidly improved. 



5. The great problem is how to eliminate the many, 

 and having found the few proving prepotent in trans- 

 mitting highly developed and effectively correlated in- 

 trinsic qualities, fully emphasize the value of their 

 blood and thus cause them to be widely propagated 

 and utilized. 



6. Plans for breed improvement must contemplate : 

 (a) the use of immense numbers from among which 

 to select many superior in individuality, (b) the testing 

 of the breeding power of each of those selected, and 

 (c) the retention of the blood of the very best breeders 

 for the improved breed or variety. 



7. It is easy in breeding many kinds of plants to 

 grow many individuals so that each plant has approxi- 

 mately the same conditions as each other plant, and 

 the small percentage of the best plants may be selected 

 for mother plants. 



8. It is likewise easy similarly to plant a large "fra- 

 ternity group" of. the progeny of each mother plant, 

 and by recording the value of the average plant of 

 each group have comparisons of the breeding powers, 

 the projected breeding efficiency of the respective 

 mother plants, that the most potent blood lines may be 

 retained as the improved variety. 



9. It is difficult in animal breeding to grow many 



