430 ANNUAL REPORT OF THE Off. Doc. 



virtue of his purity of breeding exceeds thai of the dam. Loss than 

 50 per cent, of those properties come from the dam, as many less aa 

 her prepotency or power to transmM her properties is less than that 

 of the sire, as a result of her mixed breeding. The preponderance in 

 properties in the progeny inherited from the sire will exceed those 

 inherited from the dam, as much as the power of the sire to transmit 

 his own properties because of his strong prepotency, exceeds that of 

 the dam to transmit hers, because of her weak prepotency. This 

 explains why, in the first instance of such matin-', the progeny hear 

 so strong a resemblance to the sire. 



The difference in blood elements at the first, as previously stated, 

 may be represented by 100. Now, since the progeny inherits far more 

 hugely in such breeding from the sire, the difference in those blood 

 elements will have been reduced more than 50 per cent. So far as the 

 sire is concerned, the progeny will be possessed of far more than 50 

 per cent, of inherited properties from him. The exact per cent, 

 represented by such inheritance cannot be exactly stated, but it 

 would be approximately correct to say that 75 per cent, of properties 

 in the progeny were inherited from the sire, which would leave 25 

 per cent, of the same to be inherited from the dam. Thus a great 

 stride has been made in the very first mating. The difference in 

 blood elements now between the Southdown sire and progeny will be 

 represented by 25 instead of 100 as at the first. 



Mate with a Southdown male again and the progeny of the second 

 generation will be possessed of approximately 90 per cent, of South- 

 down properties; of the third generation of approximately 07 per 

 cent, and of the fourth generation of approximately 09 per cent 

 The progeny of the fifth generation will, in individuality and useful 

 properties, be practically equal to pure bred Southdowns. This 

 wonderful transformation may be accomplished in five generations of 

 such breeding. In other words the entire common stock of farm 

 animals in the United States could be transformed within the time 

 named into pure breeds, that is into animals as good as pure breeds 

 for practical uses. At the present time, however, the supply of pure 

 bred sires would be far too little to accomplish such an end within 

 the time. 



Suppose that instead of pure Southdowns, grade Southdown sires 

 had been used. If the prepotency of those sires in each instance 

 exceeded that of the dams with which they were mated, then there 

 would be improvement. The improvement would be proportionate 

 to the excess of that prepotency. But even on the supposition that 

 the prepotency of each Southdown male was superior, variable ele- 

 ments would probably appear in the progeny as the outcome of these 

 elements in the sires, and these would in some instances at least 

 make improvement slower, while such sires were used, the level of 

 improvement readied would never equal that made in the former 

 instance, and' improvement would lie made very much more slowly. 

 The advantage, therefore, and profit from using only pure bred sires 

 is clearly apparent when these can be secured without excessive cost. 



Suppose, again, that the Southdown sires had been inferior in- 

 dividually, though purely bred, what would have happened? Why, 

 because of their prepotency the result of the purity of their breeding, 

 they would sustain their own individual superiority on the progeny. 

 This might not have followed in some instances because of the influ- 



