Sexual Organs of Phytophthora erythrosepiica , Pethyb . 137 
On one or two occasions a small spherical deep-staining body has been 
seen lying beside the surviving nucleus. It may represent the last 
stage of nuclear degeneration, which would indicate that the process 
may go on unaccompanied by any extrusion. On the other hand, it is 
not out of the question that it might be nucleolus, the fate of which, in 
the last stages of division, it has not been possible to trace. The 
peripheral daughter nuclei lie on a regular line very near the periphery. 
In an occasional case perfect nuclear structure may be made out in 
them, but nearly always they are evidently in a state of rapid dis¬ 
integration. The first sign of this is again a diffuse staining. They 
become drawn out tangentially, staining with safranin, but not sharply. 
In certain areas they form an almost continuous line separating the 
cytoplasm which lies inside from that outside. In other places there 
are small granules, with the same staining reactions as the disintegrating 
nuclei but of uncertain origin, which give this line a further appearance 
of continuity. Close examination of favourable sections shows moreover 
that there actually is a line—a membrane—forming a boundary between 
the two areas of cytoplasm independent of the nuclei (Figs. 22 and 23). 
The latter appear to be drawn out at the ends so as to contribute to the 
formation of the membrane, but if they contribute to it in any way it is 
probable that it is merely laid down on their inner surfaces where they 
cleave the protoplasm. Close study shows too that there is a differentia¬ 
tion in structure and staining reaction between the cytoplasm inside and 
outside. The inner is extremely thin and hyaline, staining practically not 
at all; the outer takes the orange slightly and seems of quite uniform 
structure, while the other is vacuolar. This is the zonation stage: the 
oosphere ( is now differentiated from the very scanty periplasm. 
Slides showing this condition have long been known, but their mean - 
ing and importance were misunderstood until the work was nearly finished 
(. 26 ). This was because the writer could not make up his mind that there 
was an actual membrane along the line of peripheral nuclei separating the 
cytoplasm inside from that outside. The figure was interpreted as showing 
the wandering out of the nuclei and the bodily contraction of all the 
cytoplasm to form the oosphere. In such a case there would be no peri¬ 
plasm. The next stage that one finds certainly shows an oosphere (or 
oospore, for it is usually fertilized by this time, but still with a very thin 
wall) which contains all the protoplasm of the oogonium (Fig. 27). It 
was natural to assume that it had been formed by the simultaneous con¬ 
traction of all the contents into one mass. That is not so however. 
There is a periplasm differentiated for a short time and separated from 
the oosphere by a plasma membrane. Its rapid d isappearance is no doubt 
to be explained by assuming that it has been absorbed by the oosphere, 
leaving no trace behind but the nuclei which lay on its inner margin. It 
