290 THE BREEDING OF ANIMALS 



viduals in each breed that represent near perfection in 

 the development of characters. There are many others 

 that are more or less deficient in such characters while 

 other individuals are actually mediocre. Will the indi- 

 vidual with near perfect characters reproduce other 

 individuals of the same high quality ? Will the mediocre 

 sort beget like mediocrity ? In other words, are the quali- 

 ties which have resulted from artificial selection indelibly 

 impressed on the hereditary substance of the germ-plasm 

 in such a way as to be certainly transmitted to the off- 

 spring? Exact answers to these questions cannot be 

 given without full knowledge of all the conditions, but 

 recent investigations have thrown much light on these 

 important questions. 



275. Selection within pure lines. Selection as prac- 

 ticed by man has undoubtedly resulted in marked im- 

 provement of the domestic animals. This improvement 

 is apparently transmitted, or at least it is possible by 

 continued selection to reproduce desirable characteristics. 

 By continually selecting individual breeding animals 

 which show a tendency to vary in the direction desired, 

 it has been assumeol. that the race or breed would gradu- 

 ally move in the direction of selection. ^ 



At one period in the history of Shorthorn cattle, all 

 breeders were agreed that their improvement was mainly 

 to be accomplished in the direction of increased size. 

 Consequently the animals of greatest scale were selected 

 and mated with the apparent result that the average size 

 of the breed was increased. But actually what was 

 accomplished after many generations of selection? Was 

 a new breed created? Had selection acted as a causa- 

 tive principle? The teachings of Darwin and his fol- 

 lowers has undoubtedly resulted in creating the impres- 



