1 48 Lloyd Williams. — St tidies in the Dictyotaceae . 
becomes more spherical, and a large vacuole appears in it containing 
minute fibrils similar to those shown in Figs. 11 and 12. After a time the 
spirem is more uniformly distributed over the whole surface. Fig. 11 does 
not show this very clearly, as the section is a median one, the rest of 
the spirem being in other sections. The nucleoplasm begins to diminish 
in amount ; some of it is seen as little fluffy threads attached to the spirem. 
The staining reactions are peculiar. With brazilin and picric- 
Hofifman-blue, for instance (the former being the chromatin and the latter 
the plasma stain), the spirem and the nucleolus stain reddish brown, the 
spherule yellowish red, while everything else, including the fibrils in the 
nucleolar vacuole, stain blue. Later on the spirem loses its chromatin 
reaction and colours blue like the chloroplasts. No definite conclusion 
respecting the chemistry of the nucleus can be drawn from this, but it 
is interesting to note how the nucleolus and the spirem reverse their 
respective colour reactions in the knot and the later spirem stage. 
The Split Spirem. The thread now instead of lying along the nuclear 
membrane becomes more evenly distributed through the cavity. Longi- 
tudinal fission can be seen here and there, and before long it is found to 
form two distinct threads which often twist round each other (Figs. 12 and 
13). The granules are irregular in size and more distant from each other. 
As in the preceding stage they show no special affinity for chromatin 
stains. The nucleolus stains more deeply, and shows a very big vacuole 
with inclusions. The spherule is still present, and besides the nucleole 
it is the only nuclear structure that colours with chromatin stains. The 
nucleoplasm diminishes in amount and finally disappears, being probably 
incorporated in the reticulum formed out of the split spirem. The centro- 
spheres are still very indistinct, the mother-cell is bigger and more 
vacuolated than in the preceding stage. 
The 4 Resting Stage.’ The next stage in the history of the spirem is 
difficult to make out. Instead of a comparatively small number of threads 
which are split, one sees a large number of very fine threads with numerous 
granules, very variable in size and disposition, crossing the nuclear cavity 
in all directions, and in many places appearing to form a reticulum 
(Fig. 14). Whether this appearance is due to the mere separation of the 
halves of the split spirem, with a lengthening and thinning out of the 
threads, or of this with a second split superadded, it is very difficult to 
make out. The halves undoubtedly do separate widely, and the identity 
of the constituent threads is completely lost, but a careful examination 
of a very large number of examples failed to disclose any clear evidence of 
such a second split. On this account, and after a close study of the 
prophase stage (Figs. 17-19), I have come to the conclusion that there 
is no second split at all, and that the appearance seen in Figs. 14, 15, 
is due to an alveolation of the separated halves of the chromatin thread 
