NUCLEAR OSMOSIS AS A FACTOR IN MITOSIS. 148 
“‘synapsis.”* Within the nucleus there are five bivalent chromosomes almost com- 
pletely organised, and a large spherical nucleolus. Surrounding the enlarged nuclear 
cavity there is a very distinct membrane, which shows every indication of being under 
pressure of the karyolymph. ‘The surrounding cytoplasm, which appears as a relatively 
narrow zone in section, is densely but finely granular and of a reticulate structure. 
Knveloping the whole is a fairly thick and apparently firm cell-wall. It will be seen 
that the nucleus occupies more than half the cubical volume of the cell. At this time 
the cytoplasm is perfectly uniform, with no indication of kinoplasmt having been 
differentiated. 
In fig. 2 we have represented a little later stage. Here it will at once be noticed 
that the nuclear volume has diminished considerably in size, that the amount of 
karyolymph present is not so great as that represented in the first figure. It will also 
be noticed that the width of the cytoplasmic zone has correspondingly increased. 
There is also to be seen a distinct modification in the structure of the cytoplasm, 
especially in the immediate vicinity of the nucleus. The cytoplasm in this region has 
taken on the form of fine, delicate threads which appear to radiate out a short distance 
from the nuclear membrane towards the periphery of the cell. In fig. 3 we represent 
a cell where the diminution of the karyoiymph has continued to such an extent that its 
cubical volume is less than half that shown in fig. 1. Here also we see the cytoplasm 
in the form of radiating threads; but these latter are much more sharply defined and 
longer than those shown in fig. 2. This is really the stage where the nuclear membrane 
is reported to break down in other types. But, as shown in figs. 4 and 5, this certainly 
does not occur in Disporum. It should be noted in passing that in these cells 
the characteristic multipolar arrangement is not so sharply defined as in many other 
plants, the kinoplasm taking on the form of radiations which form small tuft-like 
sheaves. The nuclear membrane remains intact, and, as indicated in figs. 4, 5, and 6, 
it gradually closes in the nuclear cavity with the diminution of the karyolymph. 
This latter, although now very much reduced in quantity, apparently still exerts a 
considerable pressure on the enveloping membrane, for the nuclear cavity is still 
spherical and turgid. 
These changes in the dimensions of the nuclear cavity are evidently gradual, but 
the point of interest is that they are always accompanied by a corresponding increase 
| in the differentiation of the surrounding cytoplasm ; for it is evident from figs. 3, 4, 5, 
| and 6 that, as the nucleus becomes smaller and smaller, the cytoplasmic radiations 
become longer and more sharply defined. In fig. 7 we have a most interesting stage. 
Here the karyolymph has diminished to such an extent that the chromosomes appear 
crowded about the nucleolus and the clear nuclear sap is hardly visible. The nuclear 
membrane is in close touch with the chromosomes for the greater part of its surface. 
* Lawson, A. A. (1911). 
+ I intend using the word “ kinoplasm” throughout this paper as a convenient term, but not, however in the 
sense in which it was first applied by StRASBURGER. 
