FAULL: DEVELOPMENT OF ASCUS. 
87 
observed that the eight nuclei of the last generation lie in close 
proximity to the plasma membrane surrounding the thick proto¬ 
plasm. As yet their walls are unformed and chromatin and centro- 
some are indistinguishable. The astral rays are long and prominent, 
but except for a different position from that represented in figure 
19 (pi. 8) they are unchanged. Figure 21 (pi. 8) presents a view 
of the condition of affairs at this time in polar view, and figure 23 
(pi. 8) of perhaps a slightly later stage. From these figures it is 
evident that the rays have now come to lie in a plane that is nearly 
parallel to the plasma membrane, that is, in a plane which stands at 
an angle of 90° to that in which they lay in the equatorial stage of 
the spindle. Indeed, they are slightly bent down towards the 
nucleus, a bending that becomes more and more accentuated. The 
writer, however, dissents from the view (Harper, ’ 97 ) that the rays 
are moving down to become the plasma membrane of the spores 
and that their movements are comparable to the movements of the 
cilia of zoospores. 
Changes in their position might be explained in part by two 
causes: (1) the outward movement of the nuclei. Thus there is a 
similar though not as extensive spreading movement of the rays at 
the end of the first and second mitoses (compare with fig. 12, 
pi. 7 and fig. 17, pi. 8). (2) Further, if the centrosome be a dynamic 
center and the rays an expression of cytoplasmic activity controlled 
by the nucleus, then they would change their position at this time, 
for now the bulk of the cytoplasm lies centrad of the centrosome, 
and it is here that aggregation and differentiation of spore plasm is 
taking place. 
It is not impossible that some of the rays pass into the plasma 
membrane surrounding the dense protoplasm as Harper (’ 99 ) has 
suggested for Lachnea scutellata. Cases have been observed in 
which the rays seem either to stop short at the membrane or to be 
absorbed by it, but generally they bend away. The same investi¬ 
gator (Harper, ’ 97 ) corroborates this last observation in the figures 
accompanying his paper on Erysiphe. Moreover, a reference to 
figures 11 and 16 (pi. 7) of this paper shows that the development 
of the rays on the membrane side is less than on the side in which 
the bulk of the protoplasm lies. 
Figures 23, 24, and 25 (pi. 8) represent the next stage, the one in 
which delimitation of the spore begins. This process is initiated by 
