139 
Meiotic Mitoses of Osmund a. 
show little or no sign of fission (PL VIII, Fig. i) ; but before the nuclear limit- 
ing membrane makes its appearance, and whilst the chromosomes, as seen 
from a polar view, are still arranged in a rosette, they show marked fission 
throughout their substance (Fig. 2). Sometimes the sides (threads) are 
homogeneous, sometimes they are beaded. By the time that the nucleus is 
bounded by a membrane some of the chromosomes have begun to lose their 
visible identity ; the split widens, and the chromatin tends to separate out 
along the fine connecting strands that join the several chromosome segments 
(Fig. 3). When the chromosome halves (threads) are practically resolved 
into small beads, the skeleton of each quondam chromosome is presented as 
a cloudy area which, in spite of its haziness, still reveals traces of its double 
character (Fig. 4). This appearance is difficult to reproduce faithfully in 
a drawing, but it is very characteristic of late telophasic stages. The hazi- 
ness gradually diffuses throughout the nucleus, owing to the spreading of 
the beads or granules (Fig. 5), until there results a faint reticulum with the 
chromatin almost entirely concentrated in the nucleoli, of which there may 
be three or more (Fig. 6). This is the so-called ‘ rest 1 which probably 
intervenes between each successive vegetative division. 
It may be difficult to discriminate between the phases of nuclei going 
into, from those coming out of, rest and entering upon prophase. They can, 
however, usually be distinguished by (1) the gradual blurring of the nuclear 
contents as the nucleus passes into rest, owing to the fragmentation of the 
chromatin into finer and finer granules as compared to the sharper definition 
and generally more active appearance exhibited by nuclei in the onset of 
prophase ; (2) the position of the recently laid down cell-wall between the 
daughter nuclei. In telophase the nuclei are more or less apposed to the 
cell-wall, and in a microscopical field of this stage the several pairs of nuclei 
can as a rule be recognized, whereas in prophase the daughter nuclei move 
away from the dividing wall towards the centre of the cell. 
The earliest indication of the inception of prophase is to be seen in the 
more active appearance of the nuclei and in the presence of a few large 
chromatic granules in the reticulum (Fig. 7). The reticulum is very distinct, 
particularly when stained with Heidenhain (Fig. 8), it having chromatic 
granules scattered throughout the meshwork, with here and there larger 
chromatic aggregations. The granules are at first distributed throughout 
the nucleus, and they then incline to cluster (Fig. 9) and are of varied sizes 
(Fig. 10). Simultaneously the reticulum gradually passes into a spireme 
thread.* 
At this stage the linin threads, containing the beads of chromatin 
situated at intervals along their lengths, tend to run in parallel pairs ; this is 
the inception of chromosome formation. The parallelisms represent the 
reassociation of the longitudinal chromosome halves (threads) which had 
separated during the preceding telophase. As prophase advances, the two 
