CONTENTS 



CHAPTER I 

 MENDELIAN INHERITANCE AND THE CHROMOSOMES 



PAGE 



Introduction. The Groups of Linked Factors and the Chromo- 

 somes 1 



The Inheritance of One Pair of Factors 8 



The Inheritance of Two or more Pairs of Factors 20 



CHAPTER II 



TYPES OF MENDELIAN HEREDITY 



Dominance and Recessiveness 27 



Manifold Effects of Single Factors 32 



Similar Effects Produced by Different Factors 36 



Modification of the Effects of Factors 38 



I. B}' Environmental Influences 38 



II. By Developmental Influences 42 



III. By the Influence of Other Factors 45 



IV. Conclusion 46 



CHAPTER III 



LINKAGE 



Examples Illustrating "Coupling" 48 



Examples Illustrating "Repulsion" 51 



Examples of Different Frequencies of Crossing Over 52 



The Mechanism of Crossing Over 59 



Double Crossing Over 62 



The Principle of Interference 64 



The Linear Arrangement of Factors shown by Linkage Relations . 64 



Linkage in Other Animals and in Plants 70 



The Reduplication Hypothesis 74 



xi 



I 



