CONTINUITY OF THE GERM-PLASM, &c. 



CONTENTS. 



PAOE 



INTRODUCTION' 165 



I. THE GEBM-PLASM 174 



1. Historical development of the theory as to the localization of the germ- 



plasm in the nucleus . . . . . . . . .174 



2. Nageli'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 sub- 



stance afforded by Nussbaum's and Gruber's experiments on re- 

 'generation 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. Nageli'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 idio- 



plasm into germ-plasm . . . . . . . . .198 



12. The regular cyclical development of the idioplasm founded upon 



phylogeny by Nageli . . . . . . . . .199 



13. It follows from phyletic considerations that the germ-cells have not 



arisen at the eiid 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 histo- 



genetic nucleoplasm . . . . . . . . . .213 



2. The expulsion of the polar bodies signifies the removal of the histo- 



genetic nucleoplasm . . . . . . . . . .214 



3. Other theories as to the significance of the polar bodies . . .214 



M 3 



