9() LIVESTOCK ON THE EAKM 



\isible. But they are there and will manifest themselves in 

 the offspring next time just as the others or those that appear 

 on the surface. The noticeable characteristics are called 

 dominant and those disappearing are called recessive. Both 

 exert their influence on the next generation. 



Resemblance and Difference. — Frequently there is a marked 

 resemblance between the members of a family. At other 

 times there is also a marked difference. One thing is very 

 pronounced and also very important in this connection, namely, 

 that with the exception of some twins there are no two indi- 

 viduals in a family or elsewhere that look alike. There is 

 always some variation. Sometimes this variation is small 

 and sometimes it is great. It is not all one way either; it is 

 on the side of improvement as well as on the side of retrogres- 

 sion. That is, some of the offspring, are better and some arc 

 not so good as their parents. The division is also about half 

 and half, a small number deviate or vary widely on either side 

 and a much larger number vary much less from the average 

 of sire and dam. This is illustrated by drawings by the 

 author in his book, "Swine," page 108. 



At first thought it may seem that if half of the offspring 

 from any parents or in any large herd are inferior to their 

 parents, this would be a bad thing in animal breeding. But 

 it is the breeder's only salvation. If half of the offspring arc 

 poorer then the other half are better and it is by means of 

 this better half that all improvement in animal breeding is 

 made. 



SELECTION 



According to the law of variation, then, some of the offspring 

 are better and others are poorer than the parents. Some of 

 1 he offspring are considerably better than the ancestors and an 

 occasional one is very much better. 



The breeder who wishes to make improvement in his ani- 

 mals selects these better ones or the ones that have the varia- 

 tion according to his idea of improvement and mates these for 

 his future animals. These then produce offspring which re- 

 volve about themselves as a center and produce both poorer 

 and better individuals from their standpoint. Thus it is that 

 improvement is made. And this improvement may be made 



