CONTENTS 



CHAP. PAGE 



INTRODUCTION V 



I THE RESTING NUCLEUS 1 



II THE GENERAL OUTLINE OF MITOSIS 8 



Prophase. Prometaphase. Metaphase. 

 First Stage of Anaphase. Second Stage of 

 Anaphase. Telophase 



in SPECIAL PROBLEMS OF MITOSIS 21 



Number, Form and Size of Chromosomes. 

 Genetically Active and Genetically Inert 

 Chromosomes. Salivary Gland Chromosomes 

 in Diptera. Sex-Chromosomes. Polyploidy 



TV THE GENERAL OUTLINE OF MEIOSIS 47 



Place of Meiosis in the Life-Cycle. Lepto- 

 tene. Zygotene. Pachytene. Diplotene. 

 Diakinesis. Prometaphase. Metaphase of 

 First Meiotic Division. Anaphase of First 

 Meiotic Division. Telophase of First Meiotic 

 Division. Second Meiotic Division 



V SPECIAL PROBLEMS OF MEIOSIS 69 



Chiasmata and Crossing-Over. Meiosis in 

 Hybrids. Univalent Chromosomes at Meiosis. 

 Meiosis in the Male Drosophila and in other 

 Diptera. Genetically determined Abnormal- 

 ities of Meiosis. Behaviour of Sex-Chromo- 

 somes at Meiosis. Meiosis in Haploid 

 Organisms. Meiosis in Polyploid Organisms. 

 Meiosis in Complex Heterozygotes 



VI CHROMOSOMES AND EVOLUTION 89 



Species -formation in Angiosperms. Origin 

 of complex Heterozygote Organisms. Origin 

 of new species in Bisexual Organisms. Forma- 

 tion of species in the genus Drosophila. 

 Conclusions 



vii 



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