MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 239 
nucleolus within this. In certain cases, as Dr. Lewis pointed 
out in 1870, the excretal zoospores do show clear areas which 
are probably of a nuclear nature, and in others either previous 
to or after treatment with reagents, and specially with Liquor 
Todi, a nucleoloid particle is rendered manifest. Without feel- 
ing justified in stating it as a positive fact, 1 am strongly in- 
clined to regard the presence or absence of a nucleus as con- 
nected in the present case rather with developmental than 
specific character. The body of the parasite varies consider- 
ably in appearance in different cases, and at different times in 
one and the same specimen, being sometimes almost homogeneous 
and in others distinctly granular. 
After continuing in full activity for some time, the zoospores 
sometimes pass into a condition in which they exhibit very free 
ameeboid changes of form, accompanied by frequent retraction 
and protrusion of flagella. Frequently connected with this stage, 
but sometimes also occurring as a mere interlude in the condition 
of maximum activity, processes of multiplication by division 
take place. Division is preceded by a temporary cessation of 
activity, the flagella being retracted and the body assuming a 
more or less spherical form (Plate XVIII, fig. 17 4). The out- 
line soon become oval, a constriction now appears transverse to 
the long axis of the body and rapidly deepens, and a new flagel- 
lum appears at either pole and begins to act with energy (Plate 
XVIII, fig. 17, 4,2). The central contraction continues to in- 
crease in depth, and ultimately the two segments remain con- 
nected merely by a narrow neck, which, due to their energetic 
struggles, is soon reduced to a thread (Plate XVIII, fig. 17, 7), 
and finally gives way, so as to allow the two twin zoospores to 
part company and swim off freely in the medium. 
In other cases a retardation of movement is the antecedent to 
the death of the zoospores, as may frequently be observed 
when unfavorable alterations are naturally or artificially taking 
place in the medium. It is in these cases that they come to 
present features causing them to agree with Stein’s description 
of those in Trichomonas. The movement ceases to be one of 
energetic rotatory advance and assumes a jerking character. 
This jerking is due to the emission of lateral pseudopodial pro- 
trusions in rapid succession. Where the emission, as is fre- 
quently the case at first, is very rapid, an appearance arises as 
though the body possessed a lateral row of cilia. As, however, 
a gradual retardation sets in, the true nature of the phenomenon 
ean be readily determined. It is now seen that distinct, slender 
pseudopodial processes, often of considerable length, are emitted 
from the side of the body, and sweeping round in a curve are 
again retracted. Sometimes two are visible at once, a fresh one 
