462 Sargant . — The Formation of the 
chromosomes during karyokinesis. Traces of their grouping 
round the nucleolus persist until the nucleolus and nuclear 
membrane disappear together (Fig. 20). The spindle appears 
at first as an irregular sheaf of fibres which quickly be- 
comes symmetrical. Figs. 21 and 22 (a — c ) show how the 
chromosomes are attached to the bundles of spindle fibres. 
The point of attachment is sometimes about the middle of 
the chromosome, sometimes near one end 1 . The segments 
untwist from each other as they are pulled apart. This 
probably accounts for their strained and knotted look just 
before separation (Fig. 23). In the diaster (Fig. 24) the 
segments are generally V-shaped, their angles directed towards 
either pole 2 . 
The large size of the spindles and the reduced number of 
chromosomes makes it fairly easy to count the latter in thick 
sections. Ambiguity often arises however from the different 
ways in which the chromosomes separate. It is sometimes 
impossible to distinguish between a single chromosome sepa- 
rating in the middle and two adjacent end-splitting ones. In 
thin serial sections one or more chromosomes are commonly 
shattered by the knife, and the fragments can seldom be 
pieced together with certainty. Nevertheless, I was able in 
fourteen cases to count twelve chromosomes in the nuclear 
plate. In many other instances from among some hundred 
spindles the question lay between eleven or twelve chromo- 
somes, and in a few it was doubtful whether there were 
twelve or thirteen. I have no instance of a number so low as 
ten or so high as fourteen being even suggested. 
The daughter nuclei first appear as two tight knots of 
chromatic ribbon. Their construction from the diaster seg- 
ments cannot be followed. Spherical drops of erythrophilous 
substance commonly appear in the cytoplasm about this 
1 A typical example of a chromosome separating from the middle is shown in 
Fig. 21. It is instructive to compare it with a similar chromosome applied to the 
nucleolus in Fig. 20. This suggests that nucleolar matter serves, if not as material 
for spindle fibres, at least to solder them to chromosomes. 
2 I have one preparation in which the diaster segments are hooked as in the 
vegetative nucleus. 
