48 
Wager, — The Nucleolus and Nuclear Division 
The equatorial plate first of all splits into two groups of daughter- 
chromosomes which separate to opposite poles of the spindle. As this takes 
place the chromosomes are distinctly seen as very short rods or granules 
(Figs. 25, 26). Whether they are actually separated from one another or 
remain more or less connected together by fine anastomosing threads I could 
not definitely determine. On arrival at the poles of the spindle they become 
aggregated together into a more or less homogeneous mass, in which the 
chromosomes can with difficulty be recognized (Fig. 27). At this stage 
the cell-plate appears across the equatorial region of the connecting fibres 
which are now very numerous. A nuclear membrane then appears, and 
the nucleus begins to open out or expand, exhibiting the chromosomes 
connected together by a deeply stained network (Fig. 28). The nucleus 
appears at this stage as if lodged in a cavity in the cytoplasm, the limiting 
layer of the nucleus or nuclear membrane apparently consisting of the 
peripheral layer of the nuclear network in close contact with the cyto- 
plasmic layer 1 . The cell-plate now gives place to the new cell-wall in 
the middle region of the figure, from which the connecting threads are 
fast disappearing, but at the periphery of the spindle the cell-plate forma- 
tion is still going on, as indicated by the prominent and deeply stained con- 
necting fibres. There is no indication whatever of any Concentration of 
the spindle-threads to form nucleoli, as Nemec states, although it is quite 
possible that a portion of them have been absorbed into the daughter- 
nuclei, and may enter into the constitution of the prominent network with 
which the chromosomes are connected. 
The chromosomes now begin to fuse together into somewhat irregular 
masses, or in some cases into a thick, irregular band or thread, still con- 
nected by a well-defined and deeply stained network of threads (Fig. 29). 
The connecting fibres in the middle region of the cell have disappeared, but 
those at the periphery of the nucleus are still very prominent. Already 
there are indications that the nucleolar masses are the centres of radiation 
for suspending fibres. This becomes very clear at a later stage, as shown 
in Fig. 31, in which the nuclei contain two and four nucleolar masses 
respectively. Around each large mass and one of the smaller ones clear 
spaces are to be seen. 
Fig. 30 shows a still further stage of chromosome fusion. In the upper 
nucleus there are now only two large nucleolar masses, and the way in which 
these have arisen by the fusion of smaller ones is shown in the lower of the 
two nuclei, in which four smaller nucleolar masses are to be seen fusing 
together in pairs. The nuclear network is still very prominent, and 
numerous granules of chromatin-like substance are visible on it. The 
1 Gr6goire and Wygaerts, Beihefte, Bot. Cent., 1903, p. 13, and Lawson, Bot. Gaz., xxx, 1903, 
p. 305, also conclude, from their observations on various plants, that the nucleus is lodged in 
a cavity similar to a cell-vacuole. 
