156 Davis . — Nuclear Studies on P cilia. 
such appearances give very little idea of the real structure. 
The four fibrillar cones are derived from and lie in the zone 
of kinoplasm which at this period is irregularly distributed, 
extending into the lobes of the spore-mother-cell. Although 
the fibrillae are most conspicuously massed in the cone-like 
bundles, they also completely envelop the nucleus, as may 
be plainly seen in sections that show a surface view (Fig. 8). 
The fibrillar cones have no bodies at their tips that might be 
considered centrosomes. On the contrary, they are generally 
sheathed by kinoplasm distinguished from the neighbouring 
cytoplasm by its freedom from granular matter and plastids. 
The larger number of fibrillae at these points may readily be 
explained by the accumulations of kinoplasm, which precede 
the development of the cones, and become evident before the 
fibrillae themselves appear. 
Morphology, as far as the writer's studies are concerned, 
presents no evidence that the accumulations of kinoplasm and 
the accompanying cones of fibrillae are developed or controlled 
by any protoplasmic elements in the cells, such as centro- 
spheres. The preparations of the spore-mother-cells have 
never presented such appearances as are found with centro- 
spheres and asters. When first visible the fibrillae are dis- 
tributed all around the nucleus ; but shortly afterwards the 
cone-like bundles develop sometimes simultaneously, but not 
infrequently in such a manner that one or two are far more 
prominent than the others. 
It is plain that the cones of fibrillae result from accumula- 
tions of kinoplasm that precede them in position around the 
nucleus. Why the kinoplasm should occupy so conspicuously 
the regions opening into the lobes of the spore-mother-cell 
seems obvious when we note the position of the nucleus. 
The nucleus, as may be seen from the figures, quite fills up 
the space common to the four lobes, and almost touches the 
cell-wall along the lines of constriction. The accumulations 
of kinoplasm most naturally then take positions of least 
resistance, and extend into the lobes of the spore- mother-cell. 
The four-rayed star is a transitory condition of prophase. 
