PROTOZOAN FAUNA OF HAY INFUSIONS 209 
reached the room temperature it was added to the sterile hay 
in the flasks. Four of these infusions were left exposed to the 
air, and four were plugged with cotton, sterilized dry at a temper- 
ature of 180° C. for one hour. 
W Infusions. The hay in these six infusions was sterilized 
exactly as in the case of the A series, but the water was not ster- 
ilized. All the flasks were plugged with sterile cotton. 
H Infusions. The water used in this series of six infusions was 
sterilized as in the case of the A series, and to this water was 
added fresh hay. Sterile cotton plugs were inserted in each 
flask. 
WH Infusions. These infusions, four in number, were made by 
simply adding fresh hay to ordinary tap water. The tops of the 
flasks were covered with inverted beakers. 
The twenty-three infusions may be tabulated as follows: 
A Series—to determine the organisms derived from the atmosphere. 
Atl, At2, Ay1, Ay2 = sterilized hay and water. Exposed to the air. 
At3 = control; sterilized hay and water. Not exposed to the air, but plugged 
with cotton. 
_ At4, Ay4 = control; sterilized hay and water. Inoculated with pure cultures 
of Paramaecium aurelia and caudatum, and also with Oikomonas. Plugged. 
W Series—to determine the organisms derived from tap water. 
Wtl, Wt2, Wt3, Wy1, Wy2, Wy3 = sterilized hay and fresh water. All the 
flasks plugged with sterile cotton. 
H Series—to determine the organisms derived from the hay. 
Ht1, Ht2, Ht3, Hy1, Hy2, Hy3 = sterilized water and fresh hay. Flasks 
plugged. 
WH Series—control. 
WHt1, WHt2, WHy1, WHy2 = fresh water and fresh hay. Mouth of flask 
covered with inverted beaker. 
The experiments were started on July 29th. The infusions 
were examined at intervals of approximately one week during 
the following six weeks, and at irregular intervals thereafter until 
November 11th, when the remaining infusions were destroyed. 
It was planned to carry the observations for six weeks, but at the 
end of this time it seemed advisable to continue certain ones 
longer. 
