152 Lloyd Williams . — Studies in the Dictyotaceae. 
division, and though more like that of the first segmentation of the spore 
there is a difference in the condition of the chromatin mass. Mottier has 
good figures of this stage (see his Figs. 8, 9). Instead of the chromosomes 
forming one large, deeply stained body, two, sometimes more, are formed. 
One is very large, irregular in form, and composed of fine fibrillae and 
granules, while the other is smaller, denser, and more suggestive of a 
nucleolus (Fig. 23). The former is undoubtedly the chromatin. In this 
condition it is exactly like a stage in the fragmentation of the nucleolus. 
A little later the chromatin fibrillae are seen to be more widely distributed 
through the nucleus (Fig. 24) ; eventually they disappear altogether. Co- 
incidently with this the reticulum becomes more and more evident and 
the nucleus increases in size (Fig. 25). 
The Second Mitosis in the Tetraspore Mother-Cell. 
The axes of the two daughter-nuclei are now parallel to each other 
and to the surface of the thallus, but at right angles to that of the stalk-cell. 
Thus a section tangential to the thallus shows both nuclei longitudinally. 
In such a section a first division spindle would also be cut longitudinally 
but it would be parallel to the axis of the stalk-cell, whereas in the stalk- 
cell division the figure would be cut across so as to give a polar view. 
During the prophase stage the chloroplasts are densely aggregated in 
the vicinity of the two nuclei, while the median plane is sharply marked 
out by their absence or scarcity. The two nuclei are somewhat flattened 
on the outer surfaces, whence radiations curve round the ends of each 
nucleus towards those of the sister nucleus. The spirem is thick and 
irregular, and it soon segments, the nucleolus at the same time going 
through the usual process of disintegration into fibrillae (Fig. 26). In both 
nuclei ‘ kinoplasmic 5 activity is confined to the nuclear surfaces remote 
from each other — those nearest the periphery of the mother-cell. It 
follows from this that in the early spindle the cones of fibres are not 
in a straight line. This has been well shown by Mottier. In a nucleus 
similar to his Fig. 12 the scattered chromosomes have been counted 
without difficulty, and here again the reduced number has been found 
to obtain. The mature spindle (Fig. 27) is an interesting object, especially 
when viewed in profile. Owing to the apparent c kinoplasmic ’ repulsion 
above described the spindle is placed against the outer side of the nucleus, 
the sister nucleus on the opposite side of the cell presenting the same 
features but reversed as to direction. Even at maturity there is frequently 
a slight curve in the figure. The centrosomes are not easy to make out, 
but the radiations are clear, and as before curved towards those of the 
sister nucleus. The spindle itself is elongated and narrow, the chromo- 
somes are curved, and countings of both oblique and polar views leave 
no doubt that the number is the reduced one. The remaining constituents — ■ 
