250 - D,. D., CUNNINGHAM. 
watched’ for in very many cases, it was never seen to take 
place. 
In many normal excreta in which Amcebe are present in con- 
siderable numbers, they are all in a state of inactivity, and more 
or less completely encysted. In such cases they may frequently 
be roused to activity by the addition of suitable media which are 
found in the same liquids which have been already indicated as 
adapted to the zoosporic bodies. Kven when seemingly most 
distinctly encysted no trace of an envelope is left behind on the 
emergence of the Amcebz, the cell-wall apparently undergoing 
complete resolution during the process. When they have 
emerged, the Amcebe do not exhibit such extreme susceptibility 
to changes in external conditions as the zoospores do, for they 
may often be seen to make excursions in the peripheral zone of 
nutritive fluid in diluted preparations without showing any 
symptoms of immediate detriment. In some cases the still and 
encysted Amcebze present in the excreta cannot be roused to 
activity by an addition of nutritive fluid. 
Like the zoospores, the Amcebe are very rapidly affected by 
the changes normally occurring in the excreta after their exit 
from the body. The rate at which this occurs is, perhaps, not 
quite so rapid as in the cases of the zoospores, but the final 
result, in so far as the vitality of the organism is concerned, is 
the same. With the increased acidity and the development of 
Oidium all activity ceases and the organisms either encyst or 
break up and disappear. When encystment occurs they remain 
for long recognisable in the medium, and may often be detected 
in the latter even after the acid fermentation has run its course, 
and has been succeeded by the alkaline one. So far as vitality is 
concerned, the result is the same, however, whether encystment 
occur or not. The acid stage is fatal to them, and they never 
revive with the development of the alkaline one. As in the 
case of the zoospores, so with the Amcebe, no reappearance ever 
seems to take place in excreta which have passed through the 
acid fermentation, unless due to the introduction of extraneous 
germs, and this although the medium, when once it has become 
alkaline, is eminently suitable to them. 
In addition to those which can be recognised as encysted or 
still Amcebze, there is another’ class of bodies frequently present 
in the excreta which were for long a subject of investigation ere 
their true nature could be determined. These bodies are, I 
believe, identical with certain of the bodies long ago observed 
by Drs. Swayne and Brittan,’ and subsequently described by 
Professor Hallier as spores in his celebrated treatise on the 
1“ Account of Certain Organic Cells peculiar to the Evacuations of 
Cholera,” ‘ Lancet,’ 1849, pp. 368—398 ; ‘ London Medical Gazette,’ 1849. 
