xiv TABLE OF CONTENTS 



PAGE 



D. The Mechanism of Mitosis . . . . . , * . . , .100 



1. Function of the Amphiaster 100 



(a) Theory of Fibrillar Contractility - . . . . 100 

 () 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 . . . . . .115 



3. Biological Significance of Amitosis , ^ . .. , . .116 



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

 Literature, II ..,,..... 121 



CHAPTER III 



THE GERM-CELLS 



A. The Ovtfm 124 



1. The Nucleus . . . . , , . . . . .125 



2. The Cytoplasm . . . . . r . . < . . ,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 Cytoplasm. Deposit of Deutoplasm . . 152 



(c) Yolk-nucleus 155 



2. Origin of the Spermatozoon . . . . . . . .160 



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



E. Staining-reactions of the Germ-nuclei ... . 175 

 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 208 



D. Fertilization in Plants 215 



E. Conjugation in Unicellular Forms .,...... 222 



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



Literature, IV. ......,...., 231 



