526 MONTGOMERY. [Vol. XV. 



('89, follicle cells of Blatta)\ de Bruyne ('97, follicle cells of 

 Nepa, Periplaneta, Meconema, Aeschna). E. B. Wilson ('96), 

 in speaking of amitosis, states : " In many cases, however, 

 no preliminary fission of the nucleolus occurs ; and Remak's 

 scheme must therefore be regarded as one of the rarest forms 

 of cell division." But the list of cases which I have given 

 shows that such cases of nucleolar division are frequent in 

 amitosis, so that I conclude that a fission of the nucleolus, if 

 not exactly typical for this mode of nuclear division, is never- 

 theless well represented and occurs here much more frequently 

 than in mitosis. Dr. E. G. Conklin has demonstrated to me 

 preparations of nucleolar division in follicle cells of Gryllus, 

 which he has kindly allowed me to mention here. 



2. Mitosis. — In karyokinesis the nucleolus may either not 

 disappear, or, and this is the most usual case, it disappears 

 before the spindle is formed. These two modes may be con- 

 sidered in turn. 



[a) The nucleolus does not disappear. — In some few cases 

 the nucleolus wanders out into the cytoplasm after the disap- 

 pearance of the nuclear membrane and may remain there for 

 some time without undergoing any change. Such cases have 

 been described by Hacker ('92a, o.^'g of Aeguorea), Wheeler ('95, 

 that of Myzostoma), H. V. Wilson ('94, ova of Tcdaviionc and 

 Hircinia), Tangl ('82, flower buds of He^nerocallis), Gjurasin 

 ('93, Pesisa), and Karsten ('93, sporangia of Psilotum). In all 

 these cases the nucleolus ultimately disappears in the cytoplasm, 

 though in Aeguorea it may be observed still in the cell body of 

 one of the blastomeres at the thirty-two cell stage, and the 

 daughter-nuclei produce their own nucleoli. (Similar are the 

 observations of Mead, '95; Hacker, '96, '97; Rosen, '95; Zimmer- 

 mann, '96; Metzner, '94; Foot '94; Poirault and Raciborski, '96.) 



In the other cases where the nucleolus does not disappear it 

 remains within the nucleus. In some of these cases it appears 

 to divide into two or more parts; in other cases it may be that 

 one of the daughter-nuclei receives the whole parent-nucleolus, 

 while in the other one a new nucleolus is produced. There are 

 a few observations which show that it sometimes divides ; thus 

 Strasburger ('82b, embryo sac of Galanthus) and Rosen ('92b, 



