340 Hartog . — On a Monadine parasitic 
forms assumed at this stage. From theoretical considerations 
I had not anticipated that the contractile vacuoles would 
be retained as such in the cell-sap of the living fungus ; but 
this was not confirmed, for they persist, and may be seen 
to arise afresh after systole by the confluence of two or three 
very minute vacuoles on their previous site (Fig. 3). 
The changes in the infested hyphae are very noteworthy. 
First of all, the microsomes diminish rapidly in number, so 
that the protoplasm becomes much more hyaline ; granules, 
with rapid Brownian motion, appear in the hitherto limpid 
cell-sap. During this stage the nuclei are unaffected, and 
owing to the decrease of the microsomes (which normally 
mask them from view) may be readily studied in the living 
state, as I have stated elsewhere 1 ; the protoplasmic currents 
persist on the walls and in the threads traversing the lumen. 
The protoplasm is gradually reduced to a granular debris , or 
finally disappears entirely. The cellulin-corpuscles are com- 
pletely unaffected, and remain to the last, which is not the 
case in the normal formation of zoospores or oospores in the 
Saprolegnieae, nor in hyphae of Achlya affected by the Chytri- 
dian Woronina polycystis. In some cases I have seen dumbell- 
aggregates of minute needle-shaped crystals in such exhausted 
hyphae. It not unfrequently happens that when a hypha is 
attacked in one part, the unaffected end protects itself by a 
transverse wall of protoplasm, which usually bulges out ; and 
the healthy part very frequently emits a narrow hypha, which 
grows thyllus-fashion into the cavity of the affected part. 
During their growth the amoeboids can migrate, leaving 
one hypha to enter another; that figured in 7 and 8 is 
obviously, from its size, not the direct transformation of a 
young zoospore. 
After the nutrient protoplasm is used up, that of the para- 
sites has become coarsely granular. Soon the pseudopodia 
are retracted, and the granules become collected into a highly 
refractive excrementitious mass, surrounded by a clear vacuole, 
1 Recherches sur la Structure des Saprolegniees, in Comptes Rendus, April 5, 
1889. 
