i 50 Murphy .— The Morphology and Cytology of the 
departed from the high road along which the remainder of the Peronosporales 
have progressed, and which leads to nothing else. 
Summary. 
The oogonial incept grows through the already formed antheridium 
and forms an oogonium at the farther side, as Pethybridge described. The 
antheridium remains permanently clasping the oogonium stalk. The term 
‘ amphigynous ' is suggested to express this condition. 
There is no fusion of male and female elements while the oogonial 
incept is within the antheridium. 
The male and female organs are always borne on separate hyphae, but 
the Fungus is homothallic. 
About two-thirds of the nuclei in both organs degenerate before 
division. 
The nuclei in the oogonium and in the antheridium divide once only, 
mitotically and simultaneously. Those in the oogonium are arranged 
during this process in the form of a hollow sphere with one in the 
centre. 
Zonation, the separation of the ooplasm from the periplasm, follows 
immediately after division. The ooplasm is uninucleate and is more 
hyaline than the periplasm, which is almost structureless. 
The peripheral nuclei and one daughter of the central nucleus degenerate 
immediately after division, as do all those of the antheridium but one, 
probably. 
A very large manocyst (receptive papilla) is found just as nuclear 
division is being completed protruding through the stalk of the oogonium 
into the antheridium. 
When the manocyst is withdrawn a short fertilization tube grows in at 
the same place and delivers one male nucleus and the greater part of the 
cytoplasm of the antheridium to the oosphere. 
The periplasm begins to disappear as soon as it is differentiated. 
It is all absorbed by the oosphere, the nuclei only being left outside. 
After fertilization there is no more left. 
The spore wall consists of three layers, the primitive wall and the 
primary and secondary endospores. There is no exospore. The sexual 
nuclei do not fuse until the wall is mature. 
The spore rests in the uninucleate condition. 
The close relationship, cytologically, of Phytophthora to Pythinm 
especially, and further to Sclerospora and Plcismopara , is pointed out. It is 
suggested that this series is a gradually ascending one, leading from the 
generalized type of sexual reproduction in the Ancylistales, where the 
whole of the contents of both organs unite to form the oospore, to the more 
specialized type of Peronospora , where a portion of the protoplasm of 
the oogonium remains permanently outside the oospore. 
