148 
ALBEET H. TUTTLE 
is represented by a conical group of fibers at each pole (fig. 13) ; 
but the most careful searching of a great many nuclei has failed 
to show connecting fibers between the daughter groups, the region 
between the groups being occupied by the faintly granular sub- 
stance of the nucleus, in which traces of linear arrangement of 
the granules (fig. 15) could at most be seen. Failure to discern 
the connecting fibers so clearly figured by Van Wisselingh may, 
of course, be due to an imperfect technique. 
During late prophase, but more frequently in early anaphase, 
what appear to be short fragments detached from the ends of the 
chromosomes are often seen. These were at first regarded as 
artifacts, but the examination of a large number of nuclei showed 
that they were naturally detached masses of chromatin which 
gradually assumed the form of independent rounded masses of 
varying size (figs. 11-15). 
As the daughter chromosomes approach the poles of the nucleus 
the latter becomes still more elongated (fig. 15), but with little 
if any increase in volume: the nuclear contour, even at this late 
anaphase, is as sharply defined as in the earlier stages of mitosis. 
Shortly after the individual chromosomes reach the pole they begin 
to assume a moniliform appearance, with an incurving of their 
proximal ends, entering upon the telophase. At this juncture 
there is a sudden disappearance (fig. 16) of the nuclear contour 
(''dissolution of the nuclear membrane ")? and there remains 
between the newly forming daughter nuclei an ill-defined, but 
distinct, faintly granular residual mass. This persistence of a 
definite boundary to the nucleus almost to the close of the mitosis 
is plainly indicated in the drawings of each of the writers cited, 
but neither of them has directed to it the attention which in my 
judgment it deserves. 
The daughter nuclei are now separated by a considerable dis- 
tance. Their rounding off is evidently followed by a sudden and 
rapid movement toward each other; the next phase is one in which 
they are closely approximated, while between them (fig. 17) may 
be seen a flattened granular mass, evidently the compressed re- 
siduum of the original nucleus. That their approach is exceed- 
ingl}^ rapid is evidenced by the fact that careful searching of a 
