498 Wager . — On Nuclear Division 
with the nucleolus at any point (see Fig. 19): in many cases 
I obtained sections in which the nucleolus had become dis- 
lodged from this cavity during the process of preparing the 
section. 
Division of the Nucleus. 
The nucleus of the basidium divides, first into two, then into 
four daughter-nuclei. The details of the division are difficult 
to make out, even with the highest powers of the microscope, 
and in Agaricus stercorarius are also somewhat obscured by 
the dense protoplasm. By careful staining and examination, 
however, it is possible to show that the division is distinctly 
karyokinetic, and that it corresponds in all its details with 
that observed in the higher plants and animals. There appear 
to be some slight differences of detail, in the earlier stages 
of division, in the two species examined. I will therefore 
describe them separately. 
In A. stercorarius the nucleus first of all increases somewhat 
in size and becomes elongated in the direction of the long axis 
of the basidium (Fig. 7). The nucleolus takes up a parietal posi- 
tion on the wall of the nucleus at its lower end. The nuclear 
network appears to become broken up into segments, which 
stain a little more deeply than before. The nuclear membrane 
at the upper end of the nucleus becomes indistinct and finally 
disappears, but the lower portion remains intact for some 
time longer. The nucleolus now begins to decrease in size, 
and takes a brighter red stain than formerly. At the same 
time the protoplasm, in the region of the nucleolus, stains 
more deeply. The dark blue chromatin-segments, which have 
been accumulating at the extreme apex of the nucleus as 
a somewhat homogeneous mass, now seem to disappear, and 
in their place a group of deeply stained red granules, or short 
rods, is to be seen (Fig. 8). These have been produced pro- 
bably by condensation of the chromatin-segments. This 
change in the nature of the chromatic elements coincides with 
a further change in the nucleolus, which gradually becomes 
smaller and loses, at the same time, its capacity for taking 
up the red stain, and stains only light blue. 
