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UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 905 
Contribution from the Bureau of Animal Industry 
JOHN R. MOHLER, Chief 
Washington, D. C. 
December 8, 1920 
PRINCIPLES OF LIVESTOCK 
BREEDING 
By 
SEWALL WRIGHT, Animal Husbandry Division 
CONTENTS 
Evolution of Animal Breeding .... 1 
Reproduction 2 
The Reproductive Cells in Relation to 
Heredity 11 
Details of Hereditary Transmission . . 15 
The Determination of Sex 23 
Page 
Mendelian Heredity in Livestock . . 30 
Heredity of Form and Function in Live- 
stock 34 
The System of Breeding 42 
Methods of Selection . 47 
The Value of Purebreds 54 
Has "been rev. 
—sec rev.ed. 
"binders at 
end of file. 
WASHINGTON 
GOVERNMENT PRINTING OFFICE 
1920 
