xii CONTENTS 



CHAPTER PAGE 



11. The case of the trihybrid 140 



12. Conclusion 143 



13. Summary 144 



VIII. REVERSION TO OLD TYPES AND THE MAKING OF NEW 

 ONES. 



1. The distinction between reversion and atavism . 146 



2. False reversion ....... 149 



a. Arrested development . . . . . 149 

 6. Vestigial structures 149 



c. Acquired characters resembling ancestral ones 150 



d. Convergent variation 



e. Regression . . . . . 



3. Explanation of reversion . . ... .151 



4. Some methods of improving old and establishing new 



types 152 



a. The method of Ballet . . . . .152 

 6. The method of Rimpau . . . . .153 



c. The method of de Vries . . . .154 



d. The method of Vilmorin 155 



e. The method of Johanssen .... 155 

 /. The method of Burbank . . . .156 

 g. The method of Mendel 157 



5. The factor hypothesis ...... 159 



a. Bateson's sweet peas ..... 160 



6. Castle's agouti guinea-pigs . . . . 163 



c. Cuenot's spotted mice . . . . . 164 



d. Miss Durham's intensified mice . . .165 



e. Castle's brown-eyed, yellow guinea-pigs . . 166 



6. Rabbit phenotypes 169 



7. The kinds of gray rabbits 171 



8. Conclusion . . 173 



IX. BLENDING INHERITANCE. 



1. The relative value of dominance and segregation . 174 



2. Imperfect dominance ...... 175 



3. Delayed dominance 177 



4. "Reversed" dominance . 178 



