Davis . — -Nuclear Studies on Pel Ha. 163 
nuclear membrane. In some instances this structure appeared 
at a distance from the nucleus, but it was suggested that 
such examples resulted from sections across an unsymmetrical 
nucleus. Their material was killed in strong spirit. 
These discoveries were well founded. There are aster-like 
structures in the cytoplasm, and they are frequently associated 
with a differentiated body that very strongly suggests a 
centrosphere. To the writer the problem of the significance 
of this manifestation is of some importance. A form which 
may have asters and centrospheres at one phase of ontogeny 
and entirely lack them at another, viz. in the spore-mother- 
cell, is deserving of careful study. 
The nuclei that pass into the lobes of the spore-mother- 
cell are relatively small. They come to lie near the centre 
of the spore, and increase rapidly in size until they have 
attained three or four times their previous diameter, as may 
be seen by comparing Fig. 16 (PL X) with Figs. 22-25 (PL XI). 
At first there is little evidence of a linin network, and the 
chromatin lies in droplets or granules irregularly distributed 
in the nuclear cavity. Later, however, the amount of chro- 
matin is very greatly increased, taking the form of large 
irregular bodies, which finally become arranged in a spirem. 
These characters of the nucleus are chiefly interesting to us 
at present as they may be correlated with the development 
and differentiation of the aster-like structures. 
Whether these are true asters or not is a problem far too 
complicated for our present study, as it involves evidence 
from phylogeny. Certainly they have every outward appear- 
ance of typical asters, and it is only when we examine their 
origin, behaviour, and fate that we may feel justified in with- 
drawing such a designation. The writer does not believe 
that these structures remain permanently in the cell through 
successive mitoses, nor is he satisfied that they divide to 
determine the poles of nuclear figures. Such behaviour is 
generally expected of asters chiefly through investigations 
on animal forms, but botanists as well have reported such 
activities in detail, notably Swingle (’97) in Sphacelaria and 
M 2 
