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THE AMEBIC AN NATURALIST [Vol. XLIV 



The one thousand stallions of the first generation produce the 

 second, of which some ten thousand or more are stud colts. Out 

 of these a second selection of one thousand stallions is made for 

 breeding purposes to produce the third generation. The stal- 

 lions of this second selection are sons of sires averaging 10.4 

 years of age, and the selection is based principally upon the per- 

 formances of their sisters, their cousins and their aunts. Don't 

 fail to note the fact that until very recent years, stallions were 

 rarely selected for breeding purposes because of their own per- 

 formances. Horse history is full of the assertions by breeders 

 that stallions intended for breeding should never be raced. 



Now we come to the critical point to which close attention 

 should be given. The one thousand stallions of the second selec- 

 tion are not the sons of the full one thousand stallions of the 

 first selection — one son for each sire. On the contrary, some 

 sires in the first selection are represented by numerous sons in 

 the second selection, while other sires in the first selection are 

 not represented at all. In other words, about one-half of the 

 first selection of sires is cut out by the second selection. This 

 weeding out of the sires of the first selection is done largely 

 after the sires themselves are dead, and is based upon the per- 

 formances of animals other than the sires of either generation. 



When we examine the sires of the first selection after the 

 weeding-out process involved in the second selection, we find 

 the sires eliminated by the second selection to have been prin- 

 cipally, though not wholly, sons of young sires; and that the 

 sires which are retained to breed on in the male line to the third 

 generation, are principally, though not wholly, sons of old sires. 

 The net result of cutting off part of the original selection by the 

 second selection is that the 500 left are sons of sires averaging 

 about 12.5 years of age. 



In due course of time a third selection of one thousand stal- 

 lions is made from the third generation for the purpose of 

 producing the fourth, and they in turn are sons of sires averag- 

 ing 10.4 years of age. But all of the stallions of the second 

 selection are not represented in the third selection. In fact 

 about one half of them are cut off. with the result that the 500 

 wtiieh are left in the second selection, after making the third 



the third selection cut off part of those originally in the second 



