xil CONTENTS 



CHAPTER IV 

 SEX INHERITANCE 



PAGE 



The Drosophila or XX-XY Type 78 



The Abraxas or WZ-ZZ Type 83 



What are Sex Factors? 90 



CHAPTER V 



THE CHROMOSOMES AS BEARERS OF HEREDITARY 



MATERIAL 



The Evidence from Embryology 108 



The Individuality of the Chromosomes 118 



The Chromosomes during the Maturation of the Germ Cells . . . 122 



Crossing Over 131 



Cytoplasmic Inheritance 135 



CHAPTER VI 



THE CORRESPONDENCE BETWEEN THE DISTRIBUTION OF 

 THE CHROMOSOMES AND OF THE GENETIC FACTORS 



Parallelism between the Distribution of Chromosomes and of Factors 140 



1. In Cases of Normal Distribution 140 



2. In Crosses between Species 141 



3. In Mutant Races 146 



4. Tetraploid Races 147 



Identity of Distribution of the X-chromosomes and of Sex- 

 linked Factors 148 



1. In Ordinary Crosses 148 



2. In Cases of Non-disjunction 149 



CHAPTER VII 

 MULTIPLE ALLELOMORPHS 



Definition of Multiple Allelomorphs 155 



Examples of Multiple Allelomorphs 155 



The Alternative Interpretations of Identical Loci and Complete 



Linkage 157 



