Lloyd Williams . — SHidies in the Dictyotaceae . 149 
and a joining together of the very fine reticulum thus produced by fine 
cross threads, so that the nucleus appears to be in a state of rest. 
The spherule now stains paler than before, then breaks up into two 
or several smaller ones, and at the close of this stage completely dis- 
appears. 
After a time the sporangium presents several striking features. The 
cytoplasmic constituents when seen in section are arranged in evident 
zones, so that the term c zonated ’ might be appropriately applied to it. 
The centrosomes and radiations are now exceedingly distinct at both 
poles, and there is a narrow zone of kinoplasm extending round the sides 
of the nucleus. This area is quite clear of chloroplasts. Immediately 
outside, and in sharp contrast to it, there is a zone of dense protoplasm 
with crowded chloroplasts which stain very deeply, generally taking more 
or less of the chromatin stain (Fig. 15). The outer region is vacuolated, 
and here the chloroplasts generally stain like the cytoplasm. This is not 
included in the figure. 
The nuclear membrane is firm and clear. At the poles it is generally 
very irregular ; the example selected to draw Fig. 15 from does not show 
this very clearly. It generally forms projections towards the centrosomes, 
and this causes a number of folds and wrinkles. Frequently a conical 
extension of the polar membrane has its apex touching the middle of the 
rod-like centrosome, the two ends of which are free. Occasionally the 
projection is truncated at the apex, and is in contact with the rod along its 
whole length. When this is viewed from the side the centrosome looks 
almost like a fold of the nuclear membrane. 
In Padina there is the same arrangement of the cytoplasm into 
concentric spheres, though perhaps not quite so pronounced as in Dictyota . 
The centrosome and radiations are very much less distinct. 
The nucleolus is spherical and somewhat deeply stained, but spongy, 
with large and small vacuoles. The only other constituent is the reticulum 
already described. 
The Prophase Stage. Very soon thick cloudy strands appear in the 
nucleus. There seems to be little, if any, diminution of the reticulum, so 
that it is not clear whether these are derived from a further condensation of 
the denser strands of the reticulum or not. As the cloudy bands assume 
a more definite form, a longitudinal split makes itself evident in them 
(Fig. 16). When these bodies have still further condensed, and assumed 
the forms of chromosomes, they are seen to be either closed rings or 
looped-up bands with their free ends crossing. This is well shown in 
Fig. 17 from Taonia. The next figure (18) represents three rather thick 
sections of a similar nucleus from Padina. These include all the chromo- 
somes, and they are uncut with the exception of the one in the extreme 
left of c, the bend joining the two halves of which is shown in section b. 
