Contents [INTRODUCTION.] [1. VARIATION UNDER DOMESTICATION.] [2. VARIATION UNDER NATURE.] [3. STRUGGLE FOR EXISTENCE.] [4. NATURAL SELECTION.] [5. LAWS OF VARIATION.] [6. DIFFICULTIES ON THEORY.] [7. INSTINCT.] [8. HYBRIDISM.] [9. ON THE IMPERFECTION OF THE GEOLOGICAL RECORD.] [10. ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS.] [11. GEOGRAPHICAL DISTRIBUTION.] [12. GEOGRAPHICAL DISTRIBUTION—continued.] [13. MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY:] [14. RECAPITULATION AND CONCLUSION.] [INDEX]