142 Farm Poultry 



between individual members of our herds and 

 flocks, although all members of a flock or herd 

 may have sprung from the mating of two indi- 

 viduals, and therefore have the same lineage- 

 It is more difficult to observe the differences 

 in wild birds and animals, yet such differences 

 exist sufficiently to show that the law of variation 

 is universal and constant in its action. It has 

 been said that "no two animals are exactly alike 

 in all respects." 



The tendency to vary is transmitted from par- 

 ents to progeny in the same way that other pecu- 

 liarities are transmitted. This has often been 

 of the greatest importance in the improvement of 

 fowls, mammals and plants. Breeders who are 

 trying to improve their stock are continually en- 

 deavoring to bring the law of heredity into force 

 so far as desirable characteristics are concerned, 

 and as continually striving to prevent the opera- 

 tion of the law so far as undesirable character- 

 istics are concerned. 



The fact that animals vary permits of an indi- 

 vidual being an improvement on its parents. If 

 this individual is allowed to transmit its good 

 characteristics, improvement may be attained. 

 Without progressive variation breeders could not 

 secure improvement. Probably all they could 

 do would be to prevent deterioration. 



If a breeder is trying to improve his flock, he 



