CONTENTS 



XI 



CHAPTER 



11. No known mechanism for impressing germplasm with 



somatic characters . . . . . 



12. Evidence for the inheritance of acquired characters 



inconclusive . 



a. Mutilations 



b. Environmental effects 



c. The effects of use or disuse 



d. Disease transmission 



13. The germplasm theory sufficient to 



facts of heredity . 



14. The opposition to Weismann . 



15. Conclusion .... 



account for the 



PAGE 



84 



86 

 87 

 88 

 91 

 92 



94 

 95 

 96 



VI. The Pure Line. 



1. The unit character method of attack 



2. Galton's law of regression 



3. The idea of the pure line 



4. Johanssen's nineteen beans 



5. Cases similar to Johanssen's pure lines 



6. Tower's potato-beetles 



7. Jennings' work on Paramecium 



8. Phenotypical and genotypical distinctions 



9. The distinction between a population and a pure line 

 10. Pure lines and natural selection . . . . 



VII. Segregation and Dominance. 



1. Methods of studying heredity . 



2. The melting-pot of cross-breeding 



a. Blending inheritance 



b. Alternative inheritance . 



c. Particulate inheritance 



3. Johann Gregor Mendel 



4. Mendel's experiments on garden peas 



5. Some further instances of Mendel's law 



6. The principle of segregation 



7. Homozygotes and heterozygotes 



8. The identification of a heterozygote . 



9. The presence and absence hypothesis 

 10. Dihybrids 



97 

 98 

 102 

 103 

 107 

 108 

 110 

 113 

 115 

 118 



120 

 120 

 121 

 121 

 121 

 123 

 124 

 128 

 130 

 131 

 132 

 132 

 133 



