46 Wager —The Nucleolus and Nuclear Division 
a different explanation, viz., that it indicates the beginning of the transfer- 
ence of nucleolar material to the nuclear thread 1 . 
The peripheral network of the resting nucleus as seen from the 
surface is shown in Fig. 2. It consists of a lightly stained network 
with numerous small chromatin granules. It stains less deeply in nuclear 
stains than the nucleolus, and is not very conspicuous in the resting 
stage. At the time that the suspending threads become more prominent, 
certain portions of the peripheral network become also more prominent 
and more deeply stained (Fig. 9), a number of thicker threads being 
visible, connected to one another by finer filaments of the original net- 
work. The impression conveyed to an observer on looking through 
a large number of such stages in the nuclear development is that the 
substance of the nucleolus is being conveyed into the surrounding threads, 
and this is borne out by observation of later stages, where the threads 
radiating from the nucleolus become larger and more definite, and stain 
exactly like the nucleolus, which at the same time is becoming smaller and 
more irregular or amoeboid in shape (Fig. 8). It is interesting to note that 
Zacharias, in his observations on the division of the nucleus in living rhizoids 
of Char a , observed that in the process the nucleolus becomes irregular 
in shape, and undergoes amoeboid changes of form, and then disappears 
just before the formation of the chromosomes. The stage of this amoeboid 
condition of the nucleolus in Chara corresponds exactly with what is 
observed in stained specimens of Phaseolus. In Phaseolus the amoeboid 
condition of the nucleolus coincides exactly with the thickening of the 
nuclear threads connected with it, and an inspection of Figs. 14 to 16 
indicates pretty clearly that as the nucleolus decreases in size the nuclear 
thread becomes more and more prominent, while still in definite continuity 
with the nucleolus, and staining reactions show that it becomes stained 
in a similar way. 
While these changes are taking place, kinoplasmic fibres appear at 
the poles of the nucleus, elongated in the direction of the future spindle. 
The nucleus contracts, and the nuclear thread tends to be drawn more 
closely around the nucleolus (Fig. 10). The nuclear wall breaks down 
gradually, and the fibres penetrate the cavity of the nucleus (Figs. 11 
and 12). This may take place before the formation of the chromosomes, 
and the spindle-fibres may come into contact with the unsegmented nuclear 
thread (Figs. 15 and 16). 
The thread then becomes bent sharply at different points, the nucleolus 
still being in connexion with it (Fig. 16), and then breaks up into short rod- 
like chromosomes. Fig. 17 indicates a portion of a nucleus at this stage, in 
which can be seen the remnant of the nucleolus and some of the chromo- 
1 The reference to the Figure in Nemec’s paper, p. 316, appears not to be correct, it seems to 
be Fig. 5, not Fig. 42, to which his description refers. 
