242 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Before the periplasm is cut off from the ooplasm, there is prob¬ 
ably a general mitosis in both oogonium and antheridium. 
The oosphere, when mature, is uninucleate; a single sperm 
nucleus and some cytoplasm are introduced through the perforation 
made by the receptive papilla. 
The receptive papilla is a differentiated portion of the egg and is, 
in consequence, strictly 'homologous with the receptive papillae of 
Vaucheria and Oedogonium. 
No such structure as an antheridial tube was observed. A con¬ 
spicuous tube from the oogonial wall to the inner margin of the 
peripheral cells is present but is entirely of oogonial origin. 
At the time the ooplasm and periplasm are separated the latter is 
divided anticlinally into a great number of cells which in surface 
view are hexagonal. Each cell contains at least one nucleus. Peri- 
plasmic cell walls are laid down on the outer surfaces of these cells. 
When these walls are mature the central mass is still well developed. 
The sperm nucleus usually makes a distinct change of direction in 
its migration. As the two nuclei approach, they invariably put out 
beaks on their anterior surfaces. These beaks, in some cases at 
least, came in contact. The two nuclei may remain pointed until 
the oospore wall is partly formed. 
During the development of the oospore, the two nuclei become 
spherical, stain less deeply and increase greatly in size. As the 
oleagenous globule assumes a central position, the nuclei are crowded 
to the periphery. They are always found close together even in the 
oldest oospores. 
These are in all probability the sexual nuclei; the reasons for this 
conclusion are stated under the subject of fertilization. 
There are indications that the central ooplasm is kinoplasmic in 
nature. If this be true, it is in direct opposition to Strasburger’s 
theory that the ripe egg is poor in kinoplasm and that an adequate 
supply of the latter is introduced from the antheridium. 
Considering the structure of the vegetative plant, its habitat and 
asexual method of reproduction, and the morphology and cytology 
of the sexual organs, Araiospora belongs with the Peronosporineae 
but should be placed between Pythium and the Saprolegniaceae. 
