CONTENTS XV 



PIGS 



1. Nuclear Segmentation. Mitosis (Flemming) ; Karyokinesis 



(Schleicher) 179 



(a) Cell division as it occurs in Salamandra maculata . .179 



First Stage. Preparation of the Nucleus for Division. 182 



Second Stage of Division 185 



Third Stage of Division 187 



Fourth Stage of Division 188 



(6) Division of the Egg-cells of Ascaris megalocephala and 



Toxopneustes lividus . 189 



(c) Division of Plant Cells 196 



(d) Historical remarks and unsolved problems concerning 



Nuclear Segmentation 199 



2. Direct Nuclear Division. Fragmentation. Amitosis . 207 



3. Endogenous Nuclear Multiplication, or the Formation of 



Multiple Nuclei 211 



III. Various methods of Cell Multiplication 213 



1. General Laws 213 



2. Review of the Various Modes of Cell Division . . . 223 



la. Equal Segmentation 224 



16. Unequal Segmentation 225 



Ic. Cell-Budding 228 



2. Partial or Merohlastic Segmentation .... 230 



3. So-called Free Cell Formation 232 



4. Division with Reduction 235 



IV. Influence of the Environment upon Cell Division. Degeneration . 239 



Literature 246 



CHAPTER VII. 



THE VITAL PROPERTIES OF THE CELL 252 



The Phenomena and Methods of Fertilisation 252 



I. The Morphology of the Process of Fertilisation . 256 



1. The Fertilisation of the Animal Egg 256 



(a) Echiuoderm Eggs 257 



(6) Eggs of Ascaris megalocephala 259 



2. The Fertilisation of Phanerogamia 263 



3. The Fertilisation of Infusoria 265 



4. The various forms of Sexual Cells ; equivalence of partici- 



pating Substances during the Act of Fertilisation ; Con- 

 ception of Male and Female Sexual Cells . . .272 



5. Primitive and Fundamental modes of Sexual Generation 



and the first appearance of Sexual Differences . . 278 

 II. The Physiology of the Process of Fertilisation . . . .290 



1. The Need of Reproduction of Cells 291 



(a) Parthenogenesis 295 



(6) Apogamy J 



2. Sexual Affinity 30 



