227 
Species of OIpidiopsis ) (Conin') Fischer . 
At the time of discharge of the sporangium the vacuoles disappear, 
while they are very evident in the zoospores themselves. The zoospores 
reach the exterior then, not, as Harper ( 15 ) described for Synchytrium 
decipiens , in the form of concentrated bits of protoplasm, but as definitely 
vacuolated structures (Fig. 35). Butler’s assumption that an increase in the 
imbibition water is necessary to the final fashioning of the zoospores seems 
to be substantiated by my sections. 
In sections stained with Gram’s stain there are seen in the vacuoles of 
the sporangia spherical or oval faintly staining bodies the nature of which 
was not determined (PI. XXIII, Fig. 22). They were not observed after the 
use of any other stain. They need further study. 
C. Sexual Organs. 
Very early in the development of the individual parasite, which is to 
become the oogonial cell, there is a noticeable difference in its staining 
reaction. While the protoplasm of all the parasites destined to give rise to 
sporangia and antheridia has a strong affinity for gentian violet, that of the 
oogonial cells shows very early a tendency to give up that stain and hold to 
the orange G. This fact enables one to recognize the young oogonial cell 
very early. 
Most of the material studied in section was that of O. vexans because 
of the larger sexual individuals and their better response to stains. In the 
youngest oogonial cell of which I could be sure, the nuclei already num- 
bered twenty-five to thirty. Some were distributed more or less irregularly 
throughout the contents, while the rest were arranged about the periphery 
embedded in a thin layer of finely granular protoplasm. 
Fig. 40, PI. XXV, represents the earliest stage seen in section in which 
both male and female cells showed. Enclosing walls have not yet formed 
and the two gametes are in close contact with each other. The nuclei of 
both individuals are undergoing mitotic division, and both show a marked 
vacuolate condition. The male cell possesses, as is the usual condition, 
proportionately more granular protoplasm. Most of the protoplasm of the 
oogonium is arranged about the periphery and contains many of the nuclei. 
Following this condition there is a rapid increase in the size of the 
gametes and in the number of nuclei. By the time the cells reach their 
mature size they are enclosed in cellulose walls. The wall of the antheridiuni 
remains smooth, while that of the oogonium soon begins to take on a 
roughened character. 
Fig. 41 shows portions of the two individuals with their walls fused 
and brace-walls formed. Already gelatinization of the common wall is 
taking place to form a fertilization pore. This can be detected by the deep 
stain of the wall at that point. The protoplasm is now more coarsely 
granular and much vacuolated, especially in the female cell. 
Q 2 
