CONTINUITY OF THE GERM-PLASM, &c.

CONTENTS.

Introduction 165
 
I. The Germ-Plasm 174
1. Historical development of the theory as to the localization of the germ-plasm in the nucleus 174
2. Nägeli’s ‘idioplasm’ is not identical with Weismann’s ‘germ-plasm’ 180
3. A retransformation of somatic idioplasm into germ-idioplasm does not take place 183
4. Confirmation of the theory as to the significance of the nuclear substance afforded by Nussbaum’s and Gruber’s experiments on regeneration in Infusoria 185
5. The nucleoplasm changes during ontogeny according to a certain law 186
6. The identity of the daughter-nuclei produced by indirect nuclear division, as assumed by Strasburger, is not necessary for my theory 187
7. The gradual decrease in complexity of the structure of the nucleus during ontogeny 190
8. Nägeli’s view on the germs (‘Anlagen’) in the idioplasm 192
9. The manner in which germ-cells arise from somatic cells 194
10. ’Embryonic’ cells in the mature organism 196
11. The rule of probability is against a retransformation of somatic idioplasm into germ-plasm 198
12. The regular cyclical development of the idioplasm founded upon phylogeny by Nägeli 199
13. It follows from phyletic considerations that the germ-cells have not arisen at the end of ontogeny 201
14. They originally arose at the beginning of ontogeny, but at a later period the time of their origin was displaced 202
15. A continuity of the germ-cells does not now exist in most cases 205
16. But there is a continuity of the germ-plasm 205
17. Strasburger’s objection to my supposition that the germ-plasm passes along distinct routes 209
18. The cell-body may remain unchanged when the nucleus is changed 210
19. It is conceivable that all somatic nuclei may contain some germ-plasm 211
II. The Significance of the Polar Bodies 212
1. The egg-cell contains two kinds of idioplasm; germ-plasm and histogenetic nucleoplasm 213
2. The expulsion of the polar bodies signifies the removal of the histogenetic nucleoplasm 214
3. Other theories as to the significance of the polar bodies 214
4. The modes of occurrence of polar bodies 217
5. Their possible occurrence in male germ-cells 219
6. There are two kinds of nucleoplasm in the male germ-cells 219
7. Polar bodies in plants 222
8. Morphological origin of polar bodies 223
III. On the Nature of Parthenogenesis 225
1. The phenomena exhibited in the maturation of the egg are identical in parthenogenetic and sexual development 225
2. The difference between parthenogenetic and sexual cells must be of a quantitative nature 226
3. The quantity of the germ-plasm determines development 227
4. The expulsion of polar bodies depends upon the antagonism between germ-plasm and ovogenetic nucleoplasm 230
5. Fertilization does not act dynamically 231
6. An insufficient quantity of germ-plasm arrests development 232
7. Relation of the nucleus to the cell 234
8. The case of the bee does not constitute any objection to my theory 234
9. Strasburger’s views upon parthenogenesis 237
10. Parthenogenesis does not depend upon abundant nutrition 239
11. The indirect causes of sexual and parthenogenetic reproduction 241
12. The direct causes 242
13. Explanation of the formation of nutritive cells 243
14. Identity of the germ-plasm in male and female germ-cells 246
Note 249