150 Dynamic Evolution 



that the same number had been added to the 

 fifth and later calves. Throughout its entire 

 length the table showed the discrimination 

 to be uniformly against the earlier births 

 and in favor of the later ones. 



First and second calves constitute fifty-one 

 per cent, of all calves in normally increasing 

 stock. In the group of cows born in 1901, 

 32.7 per cent, of the dams in their pedigrees 

 were found to be dams with their first and 

 second calves. In the group of cows born in 

 1902, the first and second calves in the pedi- 

 grees were reduced to 28.5 per cent., while in 

 the group born in 1903 they were further re- 

 duced to 22.1 per cent. The elimination of 

 earlier progeny goes on rapidly when there is 

 selection for functional superiority and there 

 is any opportunity for such elimination. 



This weeding out process, by which the 

 progeny of young dams is eliminated to im- 

 prove the stock, occurs most rapidly when 

 there are surplus animals to be disposed of, 

 and, as there are more surplus bulls than 

 there are surplus heifers, it should occur 



