CONTENTS. 



INTRODUCTION. 



SECT. 



1. The Study of Variation 



2. Alternative Methods ..... 



3. Continuity or Discontinuity of Variation 



4. Symmetry and Meristic Repetition 



5. Meristic Variation and Substantive Variation 



6. Meristic Repetition and Homology 



7. Meristic Repetition and Division . 



8. Discontinuity in Substantive Variation : Size 



9. Discontinuity in Substantive Variation : Colour and Colour-Patterns 



10. Discontinuity in Substantive Variation : Miscellaneous Examples 



11. Discontinuity in Meristic Variation : Examples .... 



12. Parallel between Discontinuity of Sex and Discontinuity in Variation 



13. Suggestions as to the nature of Discontinuity in Variation . 



14. Some current conceptions of Biology in view of the Facts of Variation 



1. Heredity. 2. Reversion. 3. Causes of Variation. 4. The 

 Variability of "useless" Structures. 5. Adaptation. 6. Natural 

 Selection. 



PAGE 



1 

 6 

 13 

 17 

 22 

 28 

 33 

 36 

 42 

 54 

 60 

 66 

 68 

 75 



PART I. 



MERISTIC VARIATION 



Linear Series 



Radial Series 



Bilateral Series ..... 

 Secondary Symmetry and Duplicity . 



CHAPTER I. Arrangement of Evidence . 

 CHAPTER II. Segments of Arthropoda 



87—422 

 423—447 

 448—473 

 474_566 



83 

 91 



