Lloyd Williams. — Studies in the Dictyotaceae. 15 1 
wide as the spindle itself (Fig. 20). There are divergent mantle-fibres 
between the spindle and the membrane — these rarely reach as far as the 
equator. The radiations and centrosomes are much fainter than during 
the post-spirem stage. Fig. 22 shows a very good centrosome from an 
oblique section ; there is a very similar one in the section containing the 
other pole. 
In many of the figures the spindle-fibres seem tense and nearly 
straight, while the mantle-fibres are lax and wavy (Fig. 20). The former 
give one the impression of having contracted and shortened till in some 
cases (not so well shown in the one drawn) the polar edges of the 
membrane are curved inwards and the centrosome is sunk within the 
gap. Here, as in the preceding mitosis, there are nucleolar fibrillae, which, 
as observed by Mottier, often stain almost as deeply as the chromosomes, 
but when a deep counterstain has been employed there is no difficulty 
in differentiating them from the chromatin. The nucleolar globule is 
nearly always present, generally at the periphery in the equatorial region. 
It always stains like the cytoplasm. 
The chromosomes, as already stated by Mottier, are sixteen in 
number, and decidedly heterotype in character. Figs. 20 and 21 show 
their form, and it seems hardly necessary to describe them in greater 
detail. Their small size makes it difficult to decide how they are placed 
on the spindle ; and whether the division is such as to bring about true 
reduction or not is for the same reason equally difficult to decide. 
In sections parallel to the surface of the thallus it happens occasionally 
that the nuclear figure is flattened so as to widen out considerably at the 
equator. In these cases the chromosomes are widely separated, and 
consequently more easily counted. 
The Anaphase Stage presents no peculiar features — the description 
of the stalk-cell division anaphase would almost apply to this. Mottier, 
however, states that chromosomes on their way to the poles often fuse 
together into larger masses. I have seen no instances of this in healthy 
cells. From the post-spirem stage onwards a large number of tetra- 
sporangia become arrested in their development, and frequently this takes 
place while the nucleus is in mitosis. In such cases the chromatin shows 
various abnormalities of structure. As a rule, however, one finds it easy to 
recognize such abnormal examples from the peculiar appearance of the 
cytoplasm. Occasionally, in the earlier stages of degeneration, there may 
be difficulty in deciding whether a phenomenon is normal or not. Here 
one has to depend entirely upon comparison of a large number of cases ; 
from such a comparison I have come to the conclusion that the fusion of 
chromosomes above spoken of never takes place excepting in degenerating 
sporangia. 
The Telophase Stage is strikingly different from that of the stalk-cell 
