666 Graham.-- Nuclear Division of Preissia commutata . 
and before any division of the chromosomes has taken place (Figs. j 6, 17), 
not more than eight chromosomes can be found. Fig. 20 probably repre- 
sents the stage just after the division of the chromosomes. A cross-section 
at metaphase corresponding to the grouping of the chromosomes seen in 
Fig. 20 represents sixteen chromosomes in polar view (Fig. 21). Fig. 22 is 
a polar view of metaphase before division of the chromosomes in which 
eight are represented. This section is cut in a slightly oblique direction. 
In the first division of the spore mother-cell in a longitudinal section of the 
spindle at anaphase, there are seen eight chromosomes. At this division 
the chromosomes are very much longer than in the somatic division. This 
number was counted so often that it is probably the correct one for the 
haploid number. The chromosomes in the vegetative cells are very small 
bodies. Fig. 19 is a longitudinal section through the mitotic figure. Here 
the chromosomes appear larger than those in any other section. By far the 
greater number of sections at metaphase appear as in Figs. 18 and 20. 
During anaphase the chromosomes elongate. When they reach the 
poles (Fig. 23) they are elliptical, but are still distinct from one another. 
Later, while still grouped at the poles, they become so crowded that it is 
impossible to distinguish individual chromosomes (Fig. 24). The elements 
of this crowded mass elongate considerably (Fig. 23) and appear as stout 
threads with clear spaces between them. Some of these thick threads are 
curved (Fig. 2 6). It is probable that all the curved threads represented in 
Figs. 25 and 2 6 are chromosomes since their number agrees with the number 
in late telophase illustrated in Figs. 23 and 24. Clear spaces between 
the stout threads are enlarged probably by the increase of nuclear sap 
(Figs. 25, 26). 
A nuclear membrane cannot be distinguished until the chromosomes 
have become more tenuous, longer, and as individual bodies have become 
lost in their union to form the reticulum of the nucleus. With the 
appearance of the nuclear membrane a nucleolus appears which is at first 
very small (Fig. 27). At this time also the chromatin is distributed on the 
linin reticulum in the form of granules, as has been described above in the 
resting cell. 
The nucleolus in the resting cell is, as has been stated, very large. In 
the resting condition and during the early stages of mitosis it may be 
spherical, irregularly rounded, or angular (Figs. 2, 3, 4, 5, 6). When using 
Flemming’s triple stain it stains deeply with the aniline-saffranin during all 
the early phases of mitosis. In all preparations which I have examined, 
up to the time of the segmentation of the spireme, the nucleolus was present, 
and in no case has it presented the appearance of being vacuolate. I have 
found no evidence that the nucleolus contributes any portion of its material 
for the formation of the spireme and chromosomes, although during the 
resting stage of the nucleus and in the early prophases of division strands 
