i66 
Davis . — Nuclear Studies on Pellia. 
centrosphere-like region. But the radiations in Pellia are 
very irregular in distribution, and variable in number. They 
are also sometimes so coarse as to resemble strands of proto- 
plasm rather than fibrillae. The centre of the aster is most 
clearly differentiated at periods previous to metaphase. At 
best it is a region of dense protoplasm, whose margin may 
stain somewhat deeply where the radiations have their origin. 
The interior of the structure is frequently granular, but 
generally homogeneously so, and there is no centrosome. 
These characters are shown in Figs. 28 and 29, the former 
being a view from above. Some granules are larger than 
others, but there is certainly no rule as to number or position. 
But the degree of differentiation described above is fre- 
quently vague, and sometimes entirely lacking. The centre 
of the aster may be merely a region where a number of radia- 
tions converge, and without further form (Figs. 27 and 30). 
As mitosis proceeds, the cytoplasmic radiations become 
less and less conspicuous, while the spindle-fibres extend and 
thicken. The former are generally absent at the metaphase, 
and the poles of the spindles (see Fig. 31) have a broad oval 
outline, and are usually entirely free from bodies that could 
suggest centrospheres or centrosomes. But it sometimes 
happens that the cytoplasmic radiations persist and form 
a bushy crown of fibrillae at the pole of the spindle, as is 
shown in Fig. 32. Such conditions remind one strongly of 
the aster in Fncus , but they are exceptional. Broad-poled 
spindles, quite lacking cytoplasmic radiations or other differen- 
tiations of kinoplasm, are the rule in the mitoses of the ger- 
minating spore. 
With the anaphase the pole of the spindle becomes more 
pointed (see Fig. 33), the fibres apparently drawing away 
from the neighbouring cytoplasm so that there may be a 
clear area around the pole. This is the period when the pole 
is most pointed, but cytoplasmic radiations seem never to be 
present. All trace of the aster is lost. 
The daughter-nuclei, when organized, lie surrounded by a 
zone of dense granular protoplasm, separating them from the 
