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 



n. THE CARRIERS OF THE HERITAGE. 



1. Introduction . . 14 



2. The cell theory 14 



3. 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 37 



3. The kinds of variation with respect to their 



a. Nature 38 



6. 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 



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