154 Davis. — Nuclear Studies on Pellia . 
until shortly before the time of sporogenesis. when it may 
be found, irregular in outline, in positions nearer to the centre 
of the cell (see PI. X, Fig. i), and evidently being carried to 
that situation by movements of the cytoplasm. The evi- 
dences in fixed material of such cytoplasmic activity are 
dense areas, strands and stream-like structures such as are 
found in cells where similar activities are known to occur. 
The nucleus is mobile, changing its form when necessary as 
it is carried to its final resting-place in the geometrical centre 
of the cell. As is shown in Figs. 2 and 3, the nucleus almost 
completely fills the space at the point of junction of the four 
lobes. 
There now follows a period of rest for several days, during 
which two events happen. Previous to this time the linin 
network has not been very conspicuous in the nucleus, but 
it now begins to stain deeply. At this time synapsis occurs 
in a marked and unmistakable form (see Fig. 3). 
Farmer recognized and described the event in detail. The 
linin material gathers in a close granular tangle at the side 
of the nucleolus, and all the rest of the interior is quite free 
from chromatin. Synapsis appears with perfect regularity 
at this period of ontogeny, agreeing with the writer’s observa- 
tions on Anthoceros (’ 99 , p. 97) and the general results of 
studies in sporogenesis for the higher plants. There is no 
more reason for regarding the phenomenon as an artefact 
than in Anthoceros , where the conditions for a comparative 
study of the effects of fixing fluids on the cells were most 
favourable. 
The nucleus, on emerging from synapsis, presents a delicate, 
closely wound spirem-thread with a single row of deeply 
staining granules imbedded in the linin material. The seg- 
mentation of the spirem-thread and formation of the chromo- 
somes proceed immediately, but we shall defer for the present 
the discussion of those phenomena. 
With the spirem-condition, as is shown in Fig. 4. we find 
the nucleus ready to enter the early prophase of the first 
mitosis. The nucleolus becomes vacuolate, and finally frag- 
