THE VITAL PHENOMENA OF THE CELL 199 



fibrils disappear, first around the daughter-nuclei, and then also 

 in the neighbourhood of the cellulose partition wall. 



The minute, definite particles, which collect as granules in the 

 middle of the connecting fibrils, and form a cell plate, may be 

 designated as cell-wall formers, in accordance with the above- 

 mentioned conception, which will be entered into at more detail 

 later on. 



d. Historical remarks and unsolved problems concern- 

 ing nuclear segmentation. In the commencement of the year 

 1870, in consequence of the labours of Biitschli (VII. 6), Stras- 

 burger (VI. 71), Hertwig (VI. 30a), and Fol (VI. 19a), the 

 changes experienced by the nucleus during division were 

 described on the whole correctly, although somewhat vaguely. 

 The fibrillous nuclear spindle, the collection of shining granules, 

 which is stained with carmine, in its centre (Strasburger's nuclear 

 plate), the subsequent division of the granules into two groups, or 

 two daughter nuclear plates, and the development of the vesicular 

 daughter nuclei from these latter, had all been discovered by then. 

 Further, the radiation figures stars, or amphiaster (Fol) at the 

 ends of the spindle were known, arid Fol and myself had already 

 described the presence of more strongly glistening granules, the 

 centrosomes, in them ; diagrams had been made of them, and 

 their functioning as attraction centres had been pointed out. 

 Further it had been satisfactorily established that during cell- 

 division the nucleus did not become dissolved (karyolysis, 

 Auerbach, VI. 2a), but became metamorphosed. Further, 

 through my investigations on mature eggs, especially on those of 

 Asteracanihion and Nephelis, and in consequence of the discovery 

 of the internal phenomena which occur during fertilisation, I 

 showed, at the same time, that the nucleus is not a new develop- 

 ment in the egg, but that it is derived from definite portions of the 

 germinal vesicle, which united themselves with the male pro- 

 nucleus, derived from the head of the spermatozoon (the altered 

 nucleus of the sperm cell), to form the division nucleus. As a 

 result, the important proposition was formulated that all nuclei 

 may be traced back in an unbroken line of descent from the 

 nucleus of the egg-cell, just as all cells of the animal organism 

 are derived from a fertilised egg-cell (Omnis nucleus e nucleo. 

 Flemming VI.). 



The theory of nuclear and cell division, which was founded in 

 consequence of the above-mentioned investigations, has been 



