398 TRANSACTIONS AND PROCEEDINGS OF [Sess. lvi. 



weakening not occur in the extra-nuclear centre, then the 

 latter will be able by its tilaineuts to exert a stronger pull 

 on the various nuclear elements, and arrange these round 

 its own centre, or rather two centres, as normally two para- 

 nuclei can be found in a resting-cell. In attracting the 

 nuclear elements, I would expect the extra-nuclear centre to 

 aftect, firstly, the essential intra-nuclear trophic centre, and 

 only, secondarily, the chromatin -segments, &c. That such a 

 hypothesis as just propounded, is not only possible, but highly 

 probable, seems to be proved by F. Hermann's figures and 

 description * of cell-division, which the author has studied 

 in the spermatocytes of Salamandra maculata. During the 

 resting condition of the cell a mass of " archoplasm " is to be 

 found near the nucleus, sending indistinct fibrils into the 

 body-plasm of the cell, but not showing a centrosome. (This 

 body has been, however, observed by the same author in the 

 spermatocytes of Proteus aiiguinis.) During the spirem stage 

 two centrosomes are seen, and these, as karyokinesis progresses, 

 move asunder, remaining, however, in connection with one 

 another by strands of very delicate fibrils. Simultaneously, 

 the nuclear membrane is dissolved gradually, but before its 

 complete disappearance, the chromatin-elements of the nucleus 

 occupy a i)osition in the nucleus diametrically opposite to the 

 region in which the two archoplasms and the centrosomata 

 occur. This massing together of the chromatin leads to the 

 achromatic portion of the nucleus being brought in contact 

 with the archoplasm, and it is possible to see the achromatic- 

 fibrils of the nucleus running towards the archoplasm. 



How this retraction of the chromatin-filaments is brought 

 about is, of course, a difficult cpiestion, and the author, not 

 believing in an active mobility of the chromatin-segments, 

 suggests that at that pole of the nucleus which is in close 

 contact with the archoplasm, the continuity ])etween the 

 nucleus and the body-plasm gives way first, and that through 

 this dissolution of continuity, certain streaming movements 

 into the interior of the nucleus arc set up along the achro- 

 matic filaments, and that the stnsanis of fiuid force the 

 chromatin-segments against the o])])osite side of the nucleus, 

 where as yet the nuclear mendjrane is not dissolved, and 



* IicitiMf,' ■/.. Loluf! V. (]. Kntsth. d. Kaiyok. Spiiidi-l. 'I'al. xxxi., Aicliiv. 

 f. Mikioscop. Anal, xxxvii. p. 509. 



