No. 415.] THE STUDY OF INFUSORIA. 557 
They are inclined towards an inner vessel placed in the center 
of the first. The dimensions of the two vessels should be so 
selected that the upper ends of the cells come in contact with 
the inner vessel at about 5 mm. below its open end. From 
the inner vessel water is led by cotton-yarn siphons, S”, of 
appropriate size, into the cells. A constant-level glass siphon, 
S', is hung over the wall of the outer vessel. This prevents 
\4/ s both overflow from the cells 
and the complete exhaus- 
tion of their water. The 
inner vessel is supplied 
with water from an elevated 
bottle placed near by and 
stoppered with a two-hole 
cork. One hole carries an 
air tube, A, extending to the 
bottom. The other carries 
a siphon tube, S, whose 
outer arm dips below the 
surface of the water in the 
Fic, 2. 
inner vessel, With the bottom of the bottle placed a little lower 
than the level desired for the liquid in the inner vessel, this level 
can be kept constant by raising or lowering the air tube of the 
supplying bottle. Then water will pass over the siphon only 
when the cells withdraw it from the inner vessel. The air tube 
may conveniently consist of a funnel tube, to be used also for 
filling the bottle with water. The inner vessel and its yarn 
siphons should be protected from dust by being covered with a 
glass plate whose edge is notched to admit the siphon tube. 
In siphoning, woolen yarn has been used wherever a rapid flow 
Was desired, cotton yarn where a slower rate was needed. 
