246 D. D. CUNNINGHAM, 
change in temperature of the medium is demonstrated by the 
fact that when isolated portions are kept saturated with suitable 
fluids of an alkaline nature, such as the fluid of choleraic ex- 
creta or solution of cow-dung, the zoospores retain their activity, 
and even increase considerably in number, due to processes of 
division, for hours and even for days. This was most clearly 
shown by a prolonged series of experiments, in which the phe- 
nomena in such saturated portions, isolated beneath cover-glasses, 
were compared with those occurring in the material from which 
they were derived when left to undergo the normal course of 
changes. 
A certain degree of concentration of the basis seems also, in 
most cases, to be essential to the continued life of the zoospores, 
as while those which remained in the interspaces between the 
solids of the basis continued in uninterrupted activity, others 
which found their way by their own movements, or by the action 
of currents, into the peripheral fluid of the preparations, as a 
rule, rapidly went through the series of changes previously 
described, and passed on into disintegration. The changes 
occurring in the natural basis seem to be completely fatal to the 
zoospores, as no reappearance of them was ever observed to occur 
after the medium had, passed on into the alkaline condition, 
though, as we shall subsequently find, it is then thoroughly 
adapted to them when artificially introduced. 
The zoospores are not the only infusorial organisms which 
are prejudicially affected by the initial fermentive changes occur- 
ring in the excreta, for the amceboid bodies and the bacteria are 
similarly affected. Leaving the effects produced on the former 
for future consideration, it may be well here to examine those in 
the case of the bacteria a little more closely. The first point to 
note regarding them is that the phenomena differ from those 
observed in the case of the zoospores. ‘There is no evidence 
here of any complete destruction of the organisms. There is 
merely a temporary suppression of development succeeded by 
excessive activity of it. The phenomena are parallel to those 
occurring as the result of prolonged boiling of the medium. 
Whether, however, we are to regard the subsequent development 
as due to renewed activity in preformed bacterial elements which 
have merely passed into temporary inaction due to the state of 
the medium, or whether we are to suppose that these are de- 
stroyed, and are to regard those subsequently appearing as the 
product of spores, remains an open question. In any case, 
while there is no reappearance of zoospores, an excessive de- 
velopment of bacterial elements invariably succeeds that of 
Oidium. 
While discussing questions relative to the occurrence of 
