xii CONTENTS 



CHAPTER VIII 



Page 



Somatic Mitosis and Chromosome Individuality 143 



Somatic mitosis — Preliminary sketch of mitosis — Detailed description of 

 the behavior of the chromosomes in somatic mitosis — Chromomeres — 

 Summary — The individuality of the chromosome — The frequent persistence 

 of visible chromosome Limits in the resting reticulum — Prochromosomes — 

 Persistence of parental chromosome groups after fertilization — Size and 

 shape of chromosomes — Chromosome number — Discussion and Conclusions 

 — Bibliography 8. 



CHAPTER IX 



The Achromatic Figure, Cytokinesis, and the Cell Wall 175 



The achromatic figure — In higher plants — In animals — Intranuclear 

 figures — Origin of the figure — The mechanism of mitosis — Cytokinesis — 

 In thallophytes — In microsporocytes — In animals — Mechanism of furrowing 

 -The cell wall — The primary wall layer — Secondary and tertiary wall 

 layers — The physical nature of the cell wall — The chemical nature of the 

 cell wall — The walls of spores — Bibliography 9. 



CHAPTER X 



( )ther Modes of Nuclear Division 202 



Cyanophycea? — Protozoa — Other cases in plants — Amitosis — Amitosis and 

 heredity — Bibliography 10. 



CHAPTER XI 



The Reduction of the Chromosomes 219 



Discovery — The stage in the life cycle at which reduction occurs — The 

 meaning of reduction — Interpretations based on Weismann's theory — 

 Somatic and heterotypic mitoses compared — Modes of chromosome reduc- 

 tion — Scheme A — Scheme B — Comparison of Schemes A and B — Reduction 

 with chromosome tetrads — Numerical reduction without qualitative reduc- 

 tion — Synapsis, or chromosome conjugation — Relationship of the synaptic 

 mates — The stage at which conjugation occurs — The nature of the synaptic 

 union — Chromomeres — Other opinions on the heterotypic prophase- 

 Bibliography 11. 



CHAPTER XII 

 Fertilization 273 



Fertilization in animals — The gametes — The fusion of the gametes — 

 Fertilization in protozoa — The physiology of fertilization — Fertilization 

 in plants — Algae — Fungi — Bryophytes and pteridophytes — Gymnosperms — 

 Angiosperms — Chromosome behavior — Endosperm — Bibliography 12. 



CHAPTER XIII 



Apogamy, Apospory, and Parthenogenesis 311 



Apogamy — Apospory — Parthenogenesis in animals — Bibliography 13. 



CHAPTER XIV 



The Role of the Cell Organs in Heredity 323 



The law of genetic continuity— The role of the nucleus— The promorphology 

 of the ovum — Plastid inheritance — Aleurone inheritance — General con- 

 clusions. 



