CONTENTS 



CHAPTER PAGE 



4. Methods of studying variation 42 



5. Biometry 42 



6. Fluctuating variation 43 



7. The interpretation of variation curves ... 47 



a. Relative variability ...... 47 



b. Bimodal curves ...... 47 



c. Skew polygons ....... 50 



8. Graduated and integral variations .... 52 



9. The causes of variation ...... 52 



a. Darwin's attitude ...... 52 



b. Lamarck's attitude ...... 53 



c. Weismann's attitude . .... 55 



d. Bateson's attitude ...... 55 



IV. Mutation. 



1. The mutation theory ....... 56 



2. Mutation and fluctuation ...... 57 



3. Freaks 58 



4. Kinds of mutation ....... 59 



5. Species and varieties ....... 60 



6. Plant mutations found in nature .... 63 



7. Lamarck's evening primrose ..... 64 



8. Some mutations among animals .... 67 



9. Possible explanations of mutation .... 69 

 10. A summary of the mutation theory .... 72 



V. The Inheritance of Acquired Characters. 



1. Summary of preceding chapters ..... 74 



2. The bearing of this chapter upon genetics ... 75 



3. The importance of the question ..... 75 



4. An historical sketch of opinion ..... 76 



5. Confusion in definitions ...... 77 



6. Weismann's conception of acquired characters . . 78 



7. The distinction between germinal and somatic charac- 



ters 79 



8. What variations reappear ? . . . . .80 



9. What may cause germplasm to vary or to acquire 



new characters ? . . . . . .81 



10. Weismann's reasons for doubting the inheritance of 



acquired characters ..... 84 



