CONTENTS 



CHAPTER I 

 MENDELIAN SEGREGATION AND THE CHROMOSOIMES 



Introduction. The Groups of Linked Factors and the Chromo- 



PAGE 



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. By Environm.ental Influences 38 



II. By Developmental Influences 42 



HI. 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 jMechanism of Crossing Over 59 



Double Crossing Over ^2 



The Principle of Interference ^4 



The Linear Arrangement of Factors shown by Linkage Relations . 64 



Linkage in Other Animals and in Plants 70 



The Reduplication Hypothesis '^^ 



xi 



