70 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
varying lengths (Figs. 7, 8). ‘These rods at first have a ragged outline 
and often show a more or less distinct longitudinal split. Frequently 
the ends of the rods can be traced out into the sacculations of the 
nuclear wall. In sections through one side of the nucleus (Figs. 9, 10) 
the rods often appear to lie in distinct compartments separated from 
each other by a thin membrane. ‘This, however, is probably not the 
case. Apparently these compartments are simply outpocketings or 
sacculations of a common nuclear membrane which have been cut in 
such a way as to give the appearance of distinct vesicles. ‘The chro- 
matic rods continue to shorten and thicken and become more compact, 
each one forming a single rod-shaped chromosome. Shortly after: 
the chromatic rods appear in the nucleus, there can be distinguished 
in the cytoplasrn close to the nuclear membrane two small but well 
defined asters (Figs. 7, 8). At the center of each aster there is usually 
a very minute deeply staining granule, which is evidently the centro- 
some. It is, however, doubtful if these centrosomes are present 
when the asters first appear, for, in a number of cases where the asters 
were barely distinguishable, [ have been unable to find any centro- 
somes at the center. ‘The centrosomes when they first appear are 
very minute, but increase rapidly in size. ‘The asters always make 
their appearance on that side of the nucleus which is directed towards. 
the interzonal body, and is much flattened or even concave. Following 
Montgomery (:00, p. 294) I shall call this the distal pole, the opposite 
one being the central pole of the cell. 
Whether the centrosomes retain. their individuality during the 
resting stage, it is impossible to say, although the manner of their 
appearance during the prophase would argue against such an inter- 
pretation. If they do exist as morphological entities in the resting: 
cell, they must be so minute as to be indistinguishable. Since 1 in the 
prophase the centrosomes reappear at the distal pole while during the 
telophase of the preceding division they were at the central pole, it is 
obvious that their persistence during the resting stage involves their 
migration from the central to the distal pole through, or around the 
nucleus. 
When the two asters first appear they are always some distance 
apart, and in no case have I been able to distinguish a central spindle 
or centrodesmus between them at this stage. However, they may be 
connected to each other by the astral rays which extend out for a 
considerable distance in all directions. Surrounding the asters is a 
mass of mitochondrion from which the astral rays appear to be formed, 
but it is impossible to determine this with any certainty. As the. 
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