in Dictyota dichotoma . 171 
lying either closely applied to the nuclear membrane or at 
some little distance from it (Plate XI, Fig. 1). This rod¬ 
shaped body is the centrosome, which, together with its 
kinoplasmic radiations, I shall speak of as the centrosphere. 
The planes of the longitudinal axes of the centrosomes may 
be parallel or form various angles with each other. In Fig. 1 
the centrosome at the upper side of the nucleus is seen 
from the side, the lower from the end. Viewed from the 
pole the centrosome is always rod-shaped. The kinoplasmic 
fibres radiate in all directions into the cytoplasm, where they 
pass over into the framework of the same (Fig. 2). On the 
side next the nucleus they may run parallel with its wall 
for some distance. Near the nucleus the cytoplasm is more 
granular, with smaller meshes. It is more nearly a thread¬ 
like network than alveolar in structure, and appears with 
differential staining as kinoplasm. This very fine granular 
threadwork often extends in among the radiations of the 
centrosphere. The chloroplasts may extend close up to the 
nucleus (Fig. 3) or remain some distance from it (Fig. 2). 
As karyokinesis progresses, the centrospheres become more 
conspicuous, the number of kinoplasmic radiations undoubtedly 
increasing. 
While this is going on certain changes have taken place 
in the nucleus. At first there is present a large vacuolated 
nucleolus and a fine linin-reticulum with rather large meshes, 
upon which are arranged small and nearly uniform granules, 
all of which, as previously mentioned, are not chromatin. 
The chromatin now begins to collect into larger and some¬ 
what irregular masses that finally become the chromosomes. 
The nucleolus becomes more vacuolated and soon disappears. 
The nuclear cavity presents a more granular appearance, 
the granules staining more densely. 
The kinoplasmic fibres now penetrate the membrane of 
the nucleus and enter its cavity, while at the same time the 
polar radiations diminish in number (Figs. 2 and 3). They 
do not enter the cavity so uniformly as in Stypocaulon , but 
some proceed much in advance of others. These fibres are 
