Xll CONTENTS 



CHAPTER IV 



SEX INHERITANCE 



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The Drosophila or XX-XY Type ^ 78 



The Abraxas or WZ-ZZ, Type 83 



What are Sex Factors? A 90 



Hermaphroditism and Sex 94 



Parthenogenesis and Sex 97 



The Sex of Individuals Produced by Artificial Parthenogenesis . 108 



Sex and Secondary Sexual Characters 106 



Parasitic Castration and Secondary Sexual Characters 114 



Gynandromorphs and Sex 116 



Intersexes and Sex 124 



Triploid Intersexes in Drosophila Melanogaster 130 



Sex and Sex-determining Gametes 132 



Sex-ratios 134 



CHAPTER V 



THE CHROMOSOMES AS BEARERS OF HEREDITARY 



MATERIAL 



The Evidence from Embryology 141 



The Individuality of the Chromosomes 151 



The Chromosomes during the Maturation of the Germ Cells . . . 155 



Crossing Over 164 



Other Theories of Crossing-over 168 



Attachment of Sex-chromosomes to Autosomes 172 



Tetraploidy 174 



CHAPTER VI 



CYTOPLASMIC INHERITANCE 



The Self-perpetuating Bodies in the Cytoplasm , 182 



CHAPTER VII 



THE CORRESPONDENCE BETWEEN THE DISTRIBUTION OF^ 

 ITIE CHROMOSOMES AND OF THE GENETIC FACTORS * 1 



I;- 



Parallclism between the Distribution of Chromosomes and of Factors 187 



1. In Cases of Normal Distribution 181 



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