153 
Lloyd Williams. — Studies in the Dictyotaceae. 
mantle-fibres, nucleolar globule, and fibrils — are shown in Fig. 27 and call 
for no special comment. Mottier says that ‘ the invariable tendency of the 
chromosomes to collect and fuse into larger masses has made it impossible 
to determine accurately their number in this division. In the equatorial 
plate often only two large chromatin masses are seen (Figs. 14, 15V This 
description does not apply to the material examined by me, where the 
chromosomes remain distinct up to a late stage in metakinesis. Both in 
the prophase and spindle stages the chromosomes are clearly seen to 
be homotype in character. 
The diaster stage is of the usual type. The figure becomes very 
narrow and elongated as a rule (Fig. 38). The membrane often persists 
until the daughter chromosomes are nearly at the poles. (Mottier says it 
‘ disappears soon after the spindle is mature, generally before metakinesis/) 
The pale-staining nucleolar globule is still visible at this stage. 
The formation of the daughter-nuclei shows the same phenomena 
as in the preceding division. Here, however, the nuclei are exceedingly 
small. The radiations completely disappear. In Padina the four spore- 
nuclei within the sporangium are bigger than those of Dictyota , their 
chromatin thread is prominent during the resting period, and the cytoplasm 
is differentiated into distinct concentric spheres. 
Karyokinesis in the Germinating Tetraspore. 
The tetraspore on being liberated, instead of assuming a spherical 
form as is the case with the oosphere, is nearly always elongated and 
almost cylindrical. The position of the nucleus is indicated by a lighter 
area. Division of the nucleus takes place in twelve to sixteen hours. The 
resting nucleus is much larger than it was in the tetrasporangium. The 
condition of the cytoplasm — the greater width of the meshes and the 
separation of the plastids — shows that this is due more to distension con- 
sequent on liberation from the confined space of the tetrasporangium than 
to growth. One consequence of this is that the parts of the mitotic figure 
are much clearer here than in the sporangium. 
Before the development of the spirem the usual reticular structure 
is shown. At the same time the nucleolus has the fibrillar structure so 
frequently referred to already. The spirem (Fig. 30) is coarse and unevenly 
beaded like that of the stalk-cell division: in this case, however, it is 
accompanied by a considerable amount of fine reticulum. 
The spindle (Fig. 31) is intranuclear like the preceding ones. It 
is, however, much broader at the equator and the centrosomes and radiations 
are more prominent, a result probably of diminished pressure in the 
cytoplasm. It is a rather striking fact that no nuclear globule has been 
observed at any stage of this mitosis. 
The chromosomes have been counted in a great many figures, and they 
