xii CONTENTS 



CHAPTER PAGE 



11. The case of the trihybrid . . . . . 140 



12. Conclusion 143 



13. Summary 144 



VHI. REVERSION TO OLD TTPES AND THE MAKING OF NEW 

 ONES. 



1. The distinction between reversion and atavism . 146 



2. False reversion 149 



a. Arrested development 149 



b. Vestigial structures 149 



c. Acquired characters resembling ancestral ones 150 



d. Convergent variation 150 



e. Regression 151 



8. Explanation of reversion 151 



4. Some methods of improving old and establishing new 



types 152 



a. The method of Hallet 152 



b. The method of Rimpau 153 



c. The method of de Vries 154 



d. The method of Vilmorin 155 



e. The method of Johannsen .... 155 

 /. The method of Burbank . . . .156 

 g. The method of Mendel 157 



5. The factor hypothesis 159 



a. Bateson's sweet peas 160 



b. 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 



