CONTENTS 



CHAPTER PAGE 



I. INTRODUCTION. 



1. The triangle of life 1 



2. A definition of heredity . 4 



3. The maintenance of life . '.-. . . . 5 



4. Somatoplasm and germplasm 10 



II. THE CARRIERS OF THE HERITAGE. 



1. Introduction . . - . . ... . 14 



1. The cell theory ...... . . . . 14 



8. A typical cell 15 



4. Mitosis . 18 



5. Amitosis . 20 



6. Sexual reproduction 20 



7. Maturation . . 22 



8. Fertilization . . . .. . .. 24 



9. Parthenogenesis 26 



10. The hereditary bridge . . . ... 27 



11. The determiners of heredity 28 



12. The chromosome theory 29 



13. The enzyme theory of heredity 33 



14. Conclusion 35 



III. VARIATION. 



1. The most invariable thing in nature .... 36 



2. The universality of variation 87 



3. The kinds of variation with respect to their 



a. Nature 38 



b. Duplication 39 



c. Utility .39 



d. Direction in evolution 39 



e. Source 40 



/. Normality .40 



g. Degree of continuity . . . . .40 



h. Character 41 



i. Relation to an average standard . . .41 



j. Heritability 41 



