CONTENTS xiii 



PART IV PRACTICAL PROBLEMS 



CHAPTER PAGE 



XVI. SELECTION 577 



I. Ideals in Selection 578 



II. Historical Knowledge of the Breed Necessary . . . 579 



III. General Principles involved in Selection .... 581 



IV. Rational Selection . . 592 



XVII. SYSTEMS OF BREEDING 599 



I. Purposes in Breeding 599 



II. Grading 602 



III. Crossing or Hybridizing 608 



IV. Line Breeding . 610 



V. Inbreeding . 613 



VI. Breeding from the Best 626 



References 628 



XVIII. THE DETERMINATION OF SEX 629 



I. Theories 629 



II. Influence of Nutrition . . . . , . . .631 



III. Influence of Fertilization 632 



IV. Sex in Mammals 634 



V. The Accessory Chromosome and Sex Determination . . 634 



References 637 



XIX. PLANT BREEDING 639 



I. Advantages and Limitations 639 



II. Soil and Culture Conditions 641 



III. Systems of Planting 643 



References 651 



XX. ANIMAL BREEDING . . . 654 



I. Advantages and Disadvantages 654 



II. Fewer Characters for Selection 656 



III. Fashion .658 



IV. Show-Ring Consequences 660 



V. Testing of Sires and Dams 660 



VI. Weathering a Period of Depression and Preserving the Herd 665 



VII. Records 666 



VIII. Disposal of Surplus Females . . . . . . 672 



IX. A Market for Sires 673 



X. Community Breeding 674 



XI. The Young Breeder 675 



References 676 



XXI. DEVELOPMENT 677 



APPENDIX . . 681 



INDEX . 7 1 S 



