Sexual Organs of Phytophthora erythroseptica , Pethyb. 131 
Arrangement of the Nuclei during Division . 
In the concluding stages of nuclear degeneration the surviving nuclei 
are already arranging themselves in the form of a hollow sphere with one 
in the centre. The term ‘ zonation ’ was first used by Stevens ( 34 ) to 
describe the condition in Albugo Bliti where the nuclei are arranged about 
the sharp line of demarcation between the future ooplasm and the periplasm 
which exists during division. Here all the protoplasm is similar at this 
time and there is no dividing line until division is complete. According 
to Stevens’s own interpretation of his term in the case of A. Candida he 
would not call this the zonation stage. It is best for the sake of uniformity 
and clearness to use the term exactly in Stevens’s sense, restricting it to 
the time when there is a dividing line between the ooplasm and the 
periplasm. In the hollow sphere figure (Fig. 17) there is always one 
nucleus, if not more than one, nearer the centre than the others, which 
lie in a ring outside. Probably the most correct way to describe the 
condition would be to say that the nuclei take up positions as far as 
possible from one another. The result in most cases is one nucleus in 
the centre and the remainder around the periphery. The protoplasm is 
now very vacuolate and light-staining, and it is aggregated principally 
around the nuclei. There is somewhat more of it round the periphery 
than in the centre, and this becomes more noticeable later on. Otherwise 
it is uniform all over, within and without the ring of nuclei. There is 
no denser mass in the centre and there is no trace whatever of a differen¬ 
tiated structure or organ there. All this is in striking contrast to the 
procedure in Albugo and Peronospora , but it will be found to resemble 
Pythium very closely. In fact, except that he found no nucleus in the 
centre, Miyake’s ( 24 ) figures for Pythium de Baryanum might almost as 
well serve for this Fungus. 
As anaphase and telophase come on, the ring *of nuclei has moved 
perceptibly towards the margin (Fig. 18), so that in the normal case the 
daughter nuclei are almost, but not quite, in contact with the wall. In the 
final phase the figures seem as a rule to come into the tangential direction. 
The result is that the daughter nuclei are about equally distant from the 
margin, but it does not always happen so however. These peripheral 
nuclei begin to degenerate immediately after division, and the zonation 
stage now sets in. 
The nuclei of the antheridium behave exactly as do those of the 
oogonium, and events in both organs seem to be quite simultaneous. 
There is no regular acceleration in division as was found by Kruger ( 22 ) in 
Peronospora Ficariae> although it occurs sometimes. It is considerably 
more difficult to follow the course of events there than in the oogonium, 
as most previous workers have mentioned. The number of nuclei originally 
K % 
