Breeding 441 



teristics of the offspring. That is, so far as sex is concerned, 

 they are equal from the standpoint of heredity. As has 

 been seen, the sire contributes a germ-cell to the fertilized 

 egg, and the dam furnishes a germ-cell. Furthermore, 

 each one of these germ-cells contains a complete set of 

 characters for the new individual. Some of the characters 

 of the sire may dominate those of the dam, and with other 

 characters the reverse may be the case. With many char- 

 acters, the result is an apparent blend, or intermediate 

 between the sire on the one hand and the dam on the other. 

 The question of whether the black of the boar will domi- 

 nate the white of the sow is not a matter of sex, but of 

 the character. If one parent is better bred than the other, 

 it will for this reason be more prepotent, independent of 

 any influence of sex. The old theory that the outside and 

 external characteristics are determined by the sire and the 

 inside or functional activities by the dam has long since 

 been exploded. 



SYSTEMS OF BREEDING 



Up-grading. 



The quickest, cheapest, and surest method of live-stock 

 improvement is up-grading. It is the only method 

 adapted to those farms which do not already have pure- 

 bred, or pedigreed herds. By up-grading is meant the 

 mating of the common grade sows of the farm with a pure- 

 bred boar, continuously generation after generation. In 

 effect it means the elimination of the scrub or grade boar. 

 Successful up-grading implies that the pure-bred boar 

 selected be a good individual and that only the best gilts 

 of each pig crop be retained for breeding purposes. 



As illustrated in Fig. 19, the rate of improvement in up- 

 grading is rapid and its results certain. The first cross 



