1906] OLIVE—NUCLEAR AND CELL DIVISION OF EMPUSA 237 
considerable portion of the mass, especially that in the upper daugh- 
ter nucleus, has moved centrifugally, towards the nuclear membrane. 
We note also in the upper nucleus of this figure what appears to be . 
a thickening at the outer ends of the radiating filaments, and in the 
lower nucleus some of the radiations are seen to be double. 
I am inclined to interpret jig. 61 as a very late telophase, and as a 
near approach to a resting nucleus; between this figure, however, and 
fig. 59 there is obviously a wide gap. Such nuclei as that shown in 
fig. 61 are comparatively common, however, and without doubt repre- 
sent a stage in which the center now exists only as a focal region for the 
attachment of the chromatic fibers to the nuclear membrane. Occa- 
sionally one may see at this focal point, especially in preparations 
stained with the triple stain, a very dimly defined body, apparently a 
remnant of the old center, lying against the nuclear membrane. But 
in similar preparations stained with iron haematoxylin, the core of the 
old center seems to be entirely empty, while immediately around it a 
dense chromatic mass persists for some time. In fig. 61, for example, 
there remains hardly any visible evidence of the old center of division; 
a few conspicuous fibers and a darkly stained mass which was accu- 
mulated about the center remain, however, to mark its former posi- 
tion, and the fibers now serve apparently to attach the main mass of 
chromatin to the nuclear membrane. 
Apparently such a nucleus is ‘‘polarized,” at least in so far as there 
seems to be a special and possibly permanent focal point on the 
nuclear membrane for the chromatic materials. Whether this is cen- 
tralized in the same sense as Euglena, or permanently polarized, as in 
the case of Phyllactinia (HARPER, :05), must be settled by further 
investigation. 
We see that, from very early stages, the centrosomes in these divid- 
ing nuclei are conspicuous bodies, which grow larger and more con- 
spicuous as division progresses, and this is due, in my opinion, to the 
accumulation of nuclear materials about them. Each centrosome is 
lighter in the middle and has a darker rim (figs. 50-67), a phenomenon 
which I am convinced is partially due to refraction. But careful wash- 
ing out of the stain sometimes leaves the middle totally bleached out, 
while immediately around it some parts retain the stain. Each centro- 
some thus appears possibly to have a core of plastin and a rim of chro- 
