rpHIS BULLETIN is written in simple language for 

 -*- the man who breeds farm animals, who wants to 

 learn the rudiments of the science of breeding, and 

 how to apply them in practice. It sets forth some 

 of the known facts regarding the operation of 

 the forces of heredity. Controversial subjects are 

 avoided so far as possible. 



The reader who cares to go deeper into the study 

 of genetics is referred to textbooks on the subject, 

 and particularly to Department Bulletin No. 905, 

 " Principles of Livestock Breeding," by Sewall 

 Wright. It is published by the U. S. Department 

 of Agriculture, and is obtainable from the Superin- 

 tendent of Documents, Government Printing Office, 

 Washington, D. G., for 15 cents. 



Contribution from the Bureau of Animal Industry 



JOHN R. MOHLER, Chief 

 Washington, D. C. November, 1920 





