238 M. M. Metcatr 
during the early telophases, before the elongated nucleus has become 
dumbbell-shaped (Fig. 58), or may not have occurred by the time 
the daughter nuclei are quite distinct (Fig. 65, Pl. XIX). 
Spireme. 
Ultimatly a condition is reached in which the chromosomes are 
completely united to form a long ribbon coiled irregularly over the 
surface of the nucleus, beneath the nuclear membrane (Fig. 34, lower 
half, Pl. XVI; 67, Pl. XIX). Along the course of this ribbon, from 
very many points, threads run out to join the chromatin network. 
In the preliminary notice of this paper (Mrercatr, 1907a). I referred 
to the chromatin ribbon as a more or less compact mass. The more 
compact condition is found in animals which have been kept for a 
time in cultures, and is probably slightly abnormal. 
Resting nucleus. 
Later the ribbon breaks up into band-shaped portions of un- 
equal size, varying in number from six to sixteen (Figs. 68, 70, 
Pl. XIX; 76—79, Pl. XX). Either at first, or at some time before 
the next division of the nucleus, the chromatin masses become 
sixteen in number (Figs. 35, 37, Pl. XVI), for we find sixteen of 
them, arranged in two rows of eight each during the next anaphase, 
as described (Fig. 36, Pl. XVI). Often, in nuclei in which the 
spindle is beginning to form, sixteen chromatin masses (chromosomes) 
can be counted (Fig. 35). In other similar nuclei fewer chromatin 
masses are found, the division of some of them evidently being 
retarded (Figs. 46—48, Pl. XVIII). 
The constriction of the nucleus into two daughter nuclei con- 
nected by a thread occurs before the complete fusion of the chromo- 
somes into a ribbon. By the time this ribbon has broken into its 
smaller portions the two nuclei are far separated in the cell, being 
connected only by a very slender thread consisting of the attenuated 
nuclear membrane. 
After the separation of the chromatin ribbon into its several 
portions, the spindle for the next division begins to form as already 
described. 
The nuclear membrane has remained intact during this whole 
mitotic cycle. 
