96 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
evident. This differentiation of spore plasm becomes more and 
more pronounced from this time on. During the closing stages 
of the last mitosis the spindle grows out through the ends of the 
nuclear wall, leaving behind the nucleolus and what are perhaps 
collapsed remains of the wall. The chromatin is massed against 
the centrosomes which have come into very close relation with the 
plasma membrane of the ascus. Just what has caused this elonga¬ 
tion and just what the nature of the connection is between centro¬ 
somes and plasma membrane are difficult questions to answer. 
Fine astral rays stream out from the ends of the spindles of the last 
set and it may be possible that some of these do pass into the 
plasma membrane and then contract, the contraction resulting in 
the elongation of the spindle and the drawing of the centrosomes 
to the wall. This would explain the depressions in the plasma 
membrane adjacent to the centrosomes and their connection with 
the former (pi. 10, fig. 55). 
The explanation offered by Harper (’99) of similar depressions in 
Lachnea was that they were caused by the astral rays pulling out 
of the membrane preparatory to “ cutting ” out the spore mass. 
Obviously such an explanation assumes an exercise of considerable 
force by the rays, for unless the pull be straight in line with the 
spindle the rays are at a mechanical disadvantage. Moreover, 
unless the pull be in line with the spindle (which assumes that the 
middle rays must be very short, which is contrary to fact) the cen¬ 
ter of depression would not be adjacent to the centrosomes. 
The limiting layer of protoplasm that separates the spore plasm 
of a future spore from the epiplasm begins to form during the final 
anaphase stages of the fourth spindle (pi. 10, fig. 55). It extends 
out from the centrosome following for a way closely along the 
plasma membrane that lines the wall of the ascus. The layer is pro¬ 
gressively formed until completed at the pole opposite the centro¬ 
some. Primarily very thin, it eventually thickens and becomes 
more conspicuous. Meanwhile the walls have formed about the 
daughter nuclei and this is immediately followed by a growth 
of the nuclei resulting in the fiask shape or beaked form (pi. 10, 
fig. 56). 
As soon as the spore masses are delimited, the plasma membranes 
are developed. They are formed in the plane of the limiting layer, 
and the phenomena of their production are the same as described 
for Hydnobolites and Neotiella. 
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