Division tn the Root of Vicia Faba. 175 
substance—{this becoming the more evident during the aggre- 
gation}—and not, according to my preparations, as Dr. Mont- 
gomery states, merely wound around its surface. The 
nucleolus is the centre around which the aggregation of 
nuclear substance, which leads to the formation of the thread, 
occurs. 
Nucleolar Division—This is a very common feature. The 
rounded nucleolus (Fig. 1) loses its form, becomes elongate 
(Fig. 2), then dumb-bell shaped and finally a constriction 
occurs and two equal nucleoli are to be seen (Fig. 3). 
But the interesting feature lies in the fact that this nucleolar 
division occurs and is often complete before the slightest trace 
of any nuclear aggregation occurs, #. ¢., before any trace of a 
nuclear division (Fig. 4). Frequently, nucleolar division 
occurs during the aggregation. This can probably best be 
explained by regarding the two nucleoli as centers, around 
which aggregation occurs. There is apparently no regular- 
ity as to the exact time for nucleolar division. 
The nuclear thread is now of a bluish crimson color. Itis 
a thin, long, almost continuous thread, irregularly wound 
through the nucleus. It consists of linin material, with the 
more deeply stained chromatin granules disposed at intervals 
along its course. At one or at several points this thread can 
be seen to di into the nucleolus (Fig. 6). This is not to be 
regarded either as an exceptional phenomenon or one difficult 
to see. Every preparation of the bean root, which shows 
division at all, shows many such figures (Figs. 7, 8, 9, 10). 
This relation is retained as long as any trace of a nucleolus is 
present. The nucleolus now begins to transfer its contents 
into the nuclear thread. During the early formation of this 
thread it seems to be in connection with the nucleolus at 
many points. But as the smaller masses unite to form the 
long, almost continuous thread, it is usual to see this thread 
dip into the nucleolus at one point, though it is not uncom- 
