viii CONTENTS 



CHAPTER II 



THE BEARING OF MENDEL'S DISCOVERY ON 

 THE ORIGIN OF HEREDITY CHARACTERS 



1. Mendel's First Discovery — Segregation 11-52 



2. Mendel's Second Discovery — Independent As- 



sortment 52-59 



3. The Characters of Wild Animals and Plants 



Follow the Same Laws of Inheritance as do 

 the Characters of Domesticated Animals and 

 Plants 59-81 



a. Sexual Dimorphism 61-64 



Eosin eye color of Drosophila 61-62 



Color of the Clover Butterfly, Colias 



philodice 62-63 



Color of Papilio turnus 63 



Color pattern of Papilio polytes 63-6'i 



b. Duplication of parts 65-66 



Thorax of Drosophila 65 



Legs of Drosophila 65-66 



c. Loss of characters 66-68 



"Eyeless" of Drosophila 66-67 



Vestigial wings of Drosophila 67 



Bar eye of Drosophila 67-68 



d. Small changes of characters 68-70 



"Speck" 68 



Bristles of "club" 70 



e. Manifold effects of same factor 71 



f. Constant but trivial effects may be the 



product of factors having other vital 

 aspects 73 



