CONTENTS 



CHAPTER PAGE 



I. INTRODUCTION 13 



II. REPRODUCTION AMONG ANIMALS AND PLANTS 20 



III. THE MECHANISM OP REPRODUCTION 36 



IV. THE MECHANISM OF HEREDITY 50 



V. MATHEMATICAL CONSIDERATIONS OP INBREEDING 80 



VI. INBREEDING EXPERIMENTS WITH ANIMALS AND PLANTS 100 



VII. HYBRID VIGOR OR HETEROSIS 141 



VIII. CONCEPTIONS AS TO THE CAUSE OP HYBRID VIGOR 164 



IX. STERILITY AND ITS RELATION TO INBREEDING AND CROSS-BREEDING 188 



(X. THE R6LE OF INBREEDING AND OUTBREEDING IN EVOLUTION... 195 

 XI. THE VALUE OF INBREEDING AND OUTBREEDING IN PLANT AND 



ANIMAL IMPROVEMENT 210 



XII. INBREEDING AND OUTBREEDING IN MAN: THEIR EFFECT ON 



THE INDIVIDUAL 226 



XIII. THE INTERMINGLING OP RACES AND NATIONAL STAMINA 245 



LITERATURE 266 



