MONTGOMERY. 
[Vol. XV. 
528 
explained either by the assumption that the nucleolar substance 
unites chemically with the chromatin, or that it simply pene¬ 
trates into the meshes of the latter ; since no nucleolar 
substance appears to be united with any of the twelve chromo¬ 
somes we may conclude that it does not unite chemically with 
the chromatin, and therefore the chromosomes probably do not 
serve to carry it over into the daughter-nuclei. We may now 
briefly review the results of other observers on the mode of 
disappearance of the nucleolus during mitosis. 
It is not necessary to discuss the earlier view of O. Hertwig, 
which he has since discarded, that “ der Eikern der aus dem 
Keimblaschen frei gewordene oder ausgewanderte Keimfleck 
ist,” nor yet the view of Kolliker. Kleinenberg (’ 72 ) believes 
that the germinal spot of Hydra dissolves during mitosis ; 
Brauer (’91) finds that it breaks into fragments, of which a part 
seems to be dissolved in the cytoplasm, “ ein Theil tritt unver- 
andert nach dem Schwinden der Membran in das Eiprotoplasma 
liber.” Fick (’93, germinal spot of Amblystoma) finds that the 
nucleoli disappear at the time of the longitudinal splitting of the 
chromosomes ; and Bohm (’88) reaches the same conclusion for 
Petromyzon. Davidoff (’89, ovum of Distaplia ) concludes “ dass 
aus dem Nucleolus ein Kern mit Kernnetz, mit einem Nucleolus 
und Nucleolinus hervorgegangen ist”; and Vejdovsk^ (’88, 
Rhynchelmis ), Blochmann (’82, Neritina ), and Marshall (’92, Gre- 
garina ) conclude that the nucleoli become chromosomes. In the 
egg of Ascaris the nucleoli gradually disappear, according to most 
observers. Strasburger (’82b) first contended that the nucleolar 
substance is taken up into the nuclear filaments ; later (’88) he 
writes : “ Auf Grund meiner neueren Erfahrungen erscheint es 
mir iiberhaupt unwahrscheinlich, dass die Nucleolarsubstanz, 
auch nach ihrer Auflosung im Kernsafte, den Kernfaden als 
Nahrung dienen sollte,” and he considers that after it is 
dissolved in the nuclear sap a portion of it forms the cell 
membranes of the daughter-cells (cf. also his paper of ’93). 
Rein (’83, ova of Lepus and Cavia) finds that the nucleolus 
breaks into small fragments, which finally disappear in the 
substance of the nucleus. Pfitzner (’83, ectoderm cells of 
Hydra) terms the nucleolar substance “ prochromatin,” since 
