x CONTENTS 



CHAPTBB PACT 



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 



