CONTENTS 



CHAPTER 



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 OP 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 



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 



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