Xll 



CONTENTS 



CHAPTER PAGE 



11. The case of the trihybrid 140 



12. Conclusion 143 



13. Summary 144 



ones 



new 



Vin. Reversion to Old Types and the Making of New 



Ones. 



1. The distinction between reversion and atavism 



2. False reversion ..... 



a. Arrested development 



6. Vestigial structures .... 



c. Acquired characters resembling ancestral 



d. Convergent variation 



e. Regression ..... 



3. Explanation of reversion .... 



4. Some methods of improving old and establishing 



types 



The method of Hallet 

 The method of Rimpau . . 

 The method of de Vries . 

 The method of Vilmorin . 

 The method of Johanssen 

 The method of Burbank 

 The method of Mendel . 



5. The factor hypothesis .... 



a. Bateson's sweet peas 



Castle's agouti guinea-pigs 



Cuenot's spotted mice 



Miss Durham's intensified mice 



Castle's brown-eyed, yellow guinea-pigs 



6. Rabbit phenotypes ..... 



7. The kinds of gray rabbits 



8. Conclusion ...... 



a. 

 b. 

 c. 

 d. 

 e. 



/. 

 9- 



b. 

 c. 

 d. 

 e. 



146 

 149 

 149 

 149 

 150 

 150 

 151 

 151 



152 

 152 

 153 

 154 

 155 

 155 

 156 

 157 

 159 

 160 

 163 

 164 

 165 

 166 

 169 

 171 

 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 



