254 D. D. CUNNINGHAM, 
division may undergo arrest at almost any stage, and fusion of 
the partially differentiated bodies may then take place. The 
extreme variation in the size of the sporoids in different excreta 
thus finds an easy explanation in the processes by which they 
are formed. Where the processes of formation go on undis- 
turbed in the medium, as, for instance, where the development 
occurs in specimens beneath a cover glass, the sporoids remain 
aggregated in groups embedded in their gelatinous bases, and 
exactly resembling those described and figured by Hallier. Due, 
however, to the tenuity of the matrix, they are readily detached 
from one another, and scattered under the influence of slight 
mechanical disturbances, and hence in the excreta in their 
nutural condition it is rare to encounter any save isolated 
individuals. 
The sporoid cells thus arising by processes of division within 
the Amcebe, we have next to inquire into their subsequent his- 
tory. In cultivations of excreta, in which their development has 
been followed thus far, no further vital change appears to take 
place within them. The medium, sooner or later, seems to be- 
come unsuited to them, and they disintegrate and disappear. 
It is different, however, in the case of spores which have been 
developed within the intestinal canal of the host, for many of 
these, when exposed to favorable influences, appear to give origin 
to zoospores. ‘The phenomenon of the origin of the latter may 
frequently be observed in specimens of fresh excreta, which have 
been treated with nutritive fluid. Under such circumstances 
media, which at first contained an abundance of sporoid cells 
and no zoospores, may within a few hours be found to contain 
hardly any of the former and numbers of the latter; the pro- 
portion of zoospores present at the close of the observation 
being in direct relation to the numbers of sporoids originally 
present and the proportion in which they have subsequently 
disappeared. It is difficult precisely to follow the stages in the 
process, as it only takes place in the thicker portions of the 
preparation—the sporoid cells, as before said, being rapidly 
destroyed when washed out into the surrounding fluid—but the 
cell wall of the sporoid seems to become gradually softened and 
absorbed, and does not remain behind as distinct cyst. It has 
unfortunately never been possible continuously to follow out the 
transition of any individual Amcebe into a mass of sporoid cells, 
and the resolution of the latter into zoospores. Amcebe have 
been seen to give rise to sporoids in some cases, and the origin 
of zoospores from bodies apparently in every respect indentical 
with these has been observed in others, but a link is still wanting 
in order to render the observation quite complete. In spite of 
this, however, there can, I believe, be little doubt that the 
