404 
Philippine Journal of Science 
1919 
sap. The single granule would appear to be in the nature of 
an endosome floating free in a sac containing nuclear sap and, 
possibly, plastin. In well-differentiated specimens there appears 
to be an inlying achromatinic network upon which, in many 
cases, are distributed chromatinic granules. These granules do 
not appear in all nuclei and their presence may betoken im- 
pending nuclear division. 
The normal position of the micronucleus is at the concavity 
of the meganucleus where it fits very nicely and where the meg- 
anucleus eventually encloses it within its folds. At times it 
can be seen well sunk in the notch, and at other times it is lying 
only on the edge. It may wander out of the meganuclear notch 
(see fig. 3, i) and be found anywhere near the meganucleus or 
completely separated from it and floating alone in the endoplasm. 
Although there is good ground for believing that this animal 
forms cysts, I have been unable to identify any of them with 
certainty. Apparently they occur rarely or not at all in the 
intestinal contents and it seems likely that, after a brief free- 
swimming stage in the pond water, the ciliates round out and 
form cysts which settle on aquatic plants to be later taken in 
by other snails. In other words, apparently the conditions in 
the intestines of the host as regards food supply are sufficiently 
favorable to preclude the formation of cysts there in the general 
run of infections. 
Outside of the snail the animals die quickly under experi- • 
mental conditions. Under natural conditions it is possible that 
encystation takes place exogenously as has been suggested. 
The question of the exogenous life of Balantidium is of some 
interest from the viewpoint of preventive medicine. As regards 
Balantidium coli several observers have reported it as occurring 
free. KleineU) states that he never failed to find “Paramecium 
coli” or Trichomonas in the sewage as it passed out of St. Bar- 
tholomew’s Hospital, London. He adds that if he wanted to 
obtain numerous specimens of these organisms all that was nec- 
essary was to bottle specimens of the highly diluted sewage and 
keep them for a period of about thi'ee weeks, after which abun- 
dant organisms were available. 
Such an observation as this requires careful confirmation. In 
the first place, it practically presupposes an instance of Balantid- 
ium infections out of all proportion to those that have been 
reported. It seems highly probable here that Kleine mistook 
other members of the family Bursaridse for Balantidium. 
Conn(l) with some reservation has reported Balantidium coli as 
