1 86 Lloyd Williams . — Studies in the Dzctyotaceae . 
segmenting into the chromosomes. When, however, the latter make their 
appearance, they exhibit the longitudinal split far more clearly than do 
the chromosomes in any other division (Figs. 2, 3). At first the nucleolus 
has one or more fairly large vacuoles with a number of smaller ones ; soon, 
however, the nucleolar membrane disappears, and the bulk of the nucleolus 
is seen to consist of a large number of deeply staining fibrillae, together 
with a single, slightly staining globule (Fig. 3). During this period the 
amount of nucleoplasm is very small, and the centrospheres are less 
distinct. 
The spindle (Fig. 4) is intranuclear and narrow. There are a few 
mantle-fibres extending outwards, the spaces between which are occupied 
by a large number of the deeply stained fibrillae derived from the dis- 
integrating nucleolus. The globule is generally present either on the 
spindle- fibres or in the immediate vicinity. 
The polar view represented in Fig. 5 shows the chromosomes to be 
curved in form and clearly sixteen in number. The nucleus at this stage 
is somewhat nearer the base of the cell, and the cordate appearance shown 
in Fig. 4 is very frequently met with ; it is almost certainly due to a 
contraction of the spindle after fixation. In preparations of segmenting 
eggs depressions are frequently found at both poles of the nucleus. These 
facts confirm the observation that the spindle-fibres at this period are in 
a state of tension and that they contract on fixation. 
During the anaphase stage the spindle is still narrow, but the nuclear 
cavity is wide and the membrane is intact except at the poles. The 
centrosomes are clearer than during the preceding stage, and in most cases 
the nucleolar globule is present. When the chromosomes reach the poles 
of the spindle the membrane disappears, the lower nuclear mass remains 
in the same position or descends slightly while the upper ascends, thus 
causing the whole figure to become greatly elongated. In the telophase 
stage (Fig. 6) of the oogonial nucleus the chromosomes, now greatly 
increased in size, but still preserving their curved form, are seen to be quite 
separate from each other and sixteen in number. When they fuse they 
frequently form a thick deep-staining irregular ring in which at one 
particular stage of the fusion about eight deeply stained masses may be 
distinguished (Fig. 7). Something similar was described for the stalk-cell 
division of the tetrasporangium, but was not observed in any of the other 
mitoses. The two divisions are strikingly similar also in the fact that only 
one deeply staining mass is formed in both cases, which ultimately becomes 
the nucleolus. 
If Figs. 1, 10-13 be compared certain peculiarities of cell- wall structure 
may be observed. Although the drawings are made from preparations 
fixed and stained by different methods they all agree in showing a distinct 
difference between the membranes of the parts of the cells embedded in 
