CONTENTS. 



PAGE 



Introduction 3 



PART I. 



THE PRINCIPLES OF THE CURRENT THEORY OF SELECTION. 



A REVIEW OF THE FACTS. 



I. Selection and AIutation n 



II. Mutability and Individual Variation 16 



1. The Transmutation Theory Before Darwin 16 



2. Darwin's Selection Theory 28 



3. Wallace's Selection Theory 39 



4. The Various Forms of Variability 43 



Polymorphism, 45 ; Individual or Fluctuating Varia- 

 bility, 47 ; Spontaneous Variations, 53. 



5. The Elements of the Species 56 



The Variation of the Elementary Specific Characters, 

 60. 



6. The Mutation Hypothesis 62 



Historical Review, 62, Bateson, 63 ; Scott, 66 ; Kor- 



SCHINSKY,, 68. 



III. Selection Alone Does Not Lead to the Origin of New 



Species .'. , 71 



7. Selection in Agriculture and Horticulture 71 



Maize, 71; Results of Chance Crossings, 77; Novel- 

 ties, 78. 



8. Selective Breeding Followed by Vegetative Propagation 82 



Regression, 83. 



9. On the Duration of the Process of Selection 85 



10. Acclimatization 92 



American Maize in Baden, 95; Degeneration of 

 Races, 97. 



11. Sugar Beets 99 



