130 Murphy .— The Morphology and Cytology of the 
and smaller than a nucleus, surrounded by a clear halo without a trace 
of a nuclear membrane (Figs. 15, 16, and 36). This spherical mass becomes 
smaller and smaller and finally disappears. In the same section many 
perfect nuclei are to be found. The earliest sign of degeneration is to be 
observed in certain nuclei which still appear perfect but which stain 
more diffusely than their neighbours (Fig. 16). The same process goes 
on simultaneously in the antheridium, but naturally fewer examples are 
seen (Fig. 15). 
This observation, never before recorded in this group, emphasizes 
the relationship of Phytophthora to Saprolegnia. It is possible, however, 
that it may still be found in other members, having been overlooked 
by all workers on the Saprolegniaceae previous to 1908. Davis had 
already found it in Vancheria ( 16 ), so it is certainly not confined to the 
Saprolegniaceae alone. There is one other point that must be mentioned 
in connexion with the resemblance to Saprolegnia. Just about the time 
that the oogonium is fully grown or nearly so there appears, so regularly 
that it cannot be overlooked, an irregular break in the cytoplasm some¬ 
where between the centre of the oogonium and the stalk, often a little 
eccentric but never in contact with the wall (Fig. 12). It disappears at 
a slightly later stage without leaving a trace of its presence. It looks like 
an artifact, yet its very common and constant appearance, always at the 
same time too, seems to show that it is not. It recalls strikingly the 
breaking down of the central cytoplasm in Saprolegnia. Whatever it 
may be, it is not an ordinary case of plasmolysis. The further course of 
development has nothing more, however, in common with the Sapro¬ 
legniaceae ; it resembles more closely that of the Peronosporales, and 
especially the -Pythiaceae. 
While some of the nuclei are degenerating, the oogonium becomes 
separated from the vegetative hyphae by a thick plug in the base of the 
stalk, as Pethybridge has described. It is not known how this plug is 
formed, but it probably originates as a septufn, because a septum is found 
occasionally even in mature organs in place of a plug. The plug and the 
base of the oogonium stalk surrounding it stain with orange, while the 
remainder of the oogonium wall takes gentian violet. This is an interesting 
corroboration of the results obtained by Pethybridge ( 28 ) by micro¬ 
chemical methods. It is probably at this time also that the antheridium 
is cut off by means of septa. These cross-walls usually occur a short 
distance behind in the hyphae which bear the male organ, and occasionally 
another cell is cut off behind them, the wall of which thickens and stains 
in the same way as that of the antheridium. 
