xiv TABLE OF CONTENTS 



PAGE 



D. The Mechanism of Mitosis . loo 



1. Function of the Amphiaster ......... loo 



((^7) Theory of Fibrillar Contractility ....... 100 



{b') Other Facts and Theories ........ 106 



2. Division of the Chromosomes . • . . . . . . .112 



E. Direct or Amitotic Division . . . 114 



1. General Sketch . . . . . . . . . . . .114 



2. Centrosome and Attraction-sphere in Amitosis • "5 



3. Biological Significance of Amitosis . 116 



F. Summary and Conclusion . . . . . . . . . . .119 



Literature, II 121 



CHAPTER III 



The Germ-cells 



A. The Ovum ..124 



1. The Nucleus 125 



2. The Cytoplasm 130 



3. The Egg-envelopes 132 



B. The Spermatozoon . 134 



1. The Flagellate Spermatozoon . . . . , . . . .135 



2. Other Forms of Spermatozoa 142 



3. Paternal Germ-cells of Plants 142 



C. Origin of the Germ-cells ........... 144 



D. Growth and Differentiation of the Germ-cells 150 



1. The Ovum ............. 150 



{a) Growth and Nutrition . . . . . . . . .150 



{b) Differentiation of the C)loplasm. Deposit of Deutoplasm . '152 

 (f) Yolk-nucleus ........... 155 



2. Origin of the Spermatozoon 160 



3. Formation of the Spermatozoids in Plants . . . . . . .172 



E. Staining-reactions of the Germ-nuclei . . . . . . . . • '75 



Literature, III 177 



CHAPTER IV 



Fertilization of the Ovum 



A. General Sketch . 180 



1. The Germ-nuclei in Fertilization 181 



2. The Achromatic Structures in Fertilization 185 



B. Union of the Germ-cells . . . 196 



1. Immediate Results of Union ......... 200 



2. Paths of the Germ-nuclei .......... 202 



3. Union of the Germ-nuclei. The Chromosomes ...... 204 



C. The Centrosome in Fertilization . 20S 



D. Fertilization in Plants . . . 215 



E. Conjugation in Unicellular Forms 222 



F. Summary and Conclusion ........... 229 



Literature, IV '231 



