| | PAGE |
| 1. | Can we dispense with the principle of natural selection? | [255] |
| 2. | Nägeli’s theory of transformation from internal causes | [256] |
| 3. | A definite course of development is possible without a self-changing idioplasm | [258] |
| 4. | Conclusive importance of ‘adaptations’ | [260] |
| 5. | The structure of whales as an example of adaptation | [261] |
| 6. | Transformation takes place by the smallest steps | [264] |
| 7. | The foundation of such minute changes depends upon individual variability | [266] |
| 8. | Difficulty in accounting for variability on the supposition of a continuity of the germ-plasm | [266] |
| 9. | Previous theories by which variability has been accounted for | [267] |
| 10. | Non-transmission of acquired characters | [267] |
| 11. | Nägeli’s and Alexis Jordan’s experiments | [269] |
| 12. | Germ-plasm is only altered with great difficulty | [271] |
| 13. | The source of individual variation lies in sexual reproduction | [272] |
| 14. | The process of natural selection does not operate when asexual reproduction takes place | [274] |
| 15. | Origin of variability in unicellular organisms | [278] |
| 16. | Sexual reproduction effects combination | [279] |
| 17. | E. van Beneden’s and V. Hensen’s theory of sexual reproduction as a process of rejuvenescence | [282] |
| 18. | Theoretical objections to such a view | [283] |
| 19. | Original significance of conjugation | [286] |
| 20. | Preservation of sexual reproduction by means of heredity | [287] |
| 21. | It is lost in parthenogenesis for reasons of utility | [289] |
| 22. | Parthenogenesis prevents further transformations | [290] |
| 23. | It excludes Panmixia and thus prevents disused organs from becoming rudimentary | [291] |
| 24. | Final considerations | [294] |