662 Graham . — Nuclear Division of Preissia commutata. 
The cytoplasm in the resting cell is finely granular, and in addition 
there are coarse granules scattered through it which stain more deeply. 
Several large vacuoles are also present in the cytoplasm. The resting 
nucleus is rounded and contains a small number of delicate linin strands. 
These strands stretch across the nuclear cavity, occasionally anastomosing. 
At low magnification they seem to radiate from the nucleolus. Some of 
the chromatin granules are distributed on the linin network, either at points 
where the linin strands meet or here and there on long portions of a strand 
free from anastomosing ones. Possibly all the linin strands are not 
differentiated by the stain used. The nucleolus in the resting cell is a large 
irregular!)/ rounded body lying in the centre of the nucleus. In addition to 
this large nucleolus, a smaller one of the same general form frequently 
accompanies it (Fig. i). Conspicuous nucleoli and a delicate network of 
linin threads were described in the vegetative cells by Van Hook (' 00 ), 
who studied cell-division in the stalk of the archegoniophore of Marchantia 
polymorpha. 
The first indication of prophase is the elongation of the nucleus, usually 
in the direction of the long axis of the cell. All of the nuclear contents 
become more conspicuous. The linin increases in quantity, not only in the 
number, but also in the increased width of the strands, thus making a more 
complex and dense reticulum than the open, delicate reticulum of the 
resting cell. Large irregular chromatin masses appear in this elongated 
nucleus, either on the linin or lying apparently free in the nuclear cavity. 
These masses are formed partly by the union of the chromatin granules, 
partly from another source ; for, considering their size and number, it is 
probable that the union of the granules seen in the nucleus of the resting 
cell is not the only source through which their bulk has been increased. 
The size, staining reaction, and surface appearance of the nucleolus remain 
the same as in the resting nucleus. Therefore it cannot be said to con- 
tribute any appreciable amount of chromatic substance to the chromatin 
masses (Fig. 2). An account of the behaviour of the nucleolus in the 
vegetative cells of Preissia commutata will be given later. 
The cytoplasm at this phase of the nucleus shows a differentiation into 
areas that are finely granular and coarsely granular. The coarseness of the 
latter areas is due to a grouping of the granules that were scattered 
throughout the cytoplasm of the resting cell. This condition is shown in 
Figs. 2, 6 , and 7. 
Certain of the strands of linin forming the complex network described 
above thicken and form a more or less continuous spireme, while other 
strands anastomosing with this remain very delicate. These delicate 
strands finally disappear, fragments of them remaining for a time as lateral 
projections from the forming spireme, which thus adds to the irregular outline 
of the surface of the spireme (Figs. 3, 4, 5). The masses of chromatin 
