xii TABLE OF CONTENTS 



E. Direct or Amitotic Division 80 



1. General Sketch 80 



2. Centrosome and Attraction-sphere in Amitosis . . . . . .Si 



3. Biological Significance of Amitosis 82 



F. Summary and Conclusion <S 5 



Literature, II 8t> 



CHAPTER III 



THE GERM-CELLS 



A. The Ovum 90 



1. The Nucleus 92 



2. The Cytoplasm 94 



3. The Egg-envelopes .96 



B. The Spermatozoon . . .98 



1. The Flagellate Spermatozoon -99 



2. Other Forms of Spermatozoa . . .106 



3. Paternal Germ-cells of Plants 106 



C. Origin and Growth of the Germ-cells .108 



D. Growth and Differentiation of the Germ-cells . . . . . . .113 



1. The Ovum 113 



(a) Growth and Nutrition 113 



() Differentiation of the Cytoplasm. Deposit of Deutoplasm . . 115 



(*) Yolk-nucleus 118 



2. Formation of the Spermatozoon 122 



E. Staining-reactions of the Germ-nuclei 127 



Literature, III. 128 



CHAPTER IV 

 FERTILIZATION OF THE OVUM 



A. General Sketch -130 



1. The Germ-nuclei in Fertilization 132 



2. The Centrosome in Fertilization 135 



B. Union of the Germ-cells ........... 145 



1. Immediate Results of Union ......... 149 



2. Paths of the Germ-nuclei 151 



3. Union of the Germ-nuclei. The Chromosomes ...... 153 



C. Centrosome and Archoplasm in Fertilization . . . . . . -156 



D. Fertilization in Plants . . . . . . . . . . . .160 



E. Conjugation in Unicellular Forms . -163 



F. Summary and Conclusion 170 



Literature, IV . . . . -171 



CHAPTER V 

 REDUCTION OF THE CHROMOSOMES, OOGENESIS AND SPERMATOGENESIS 



A. General Outline 174 



1. Reduction in the Female. The Polar Bodies . . . . . 175 



2. Reduction in the Male. Spermatogenesis .180 



3. Theoretical Significance of Maturation 182 



B. Origin of the Tetrads 186 



1. General Sketch 186 



2. Detailed Evidence . .187 



< . The Early History of the Germ-nuclei ......... 193 



I). Reduction in the Plants . . . 195 



