102 C. CLIFFORD DOBELL. 
them. A drop of this is placed on the dried-up cysts on the 
coverslip, and a hanging-drop preparation made on a hollow- 
ground slide. The coverslip is carefully waxed round the 
edges, and examined from time to time. In three or four 
days monads are usually to be found swimming about and 
dividing. In preparations made in this way a large number 
of cysts never develop, and many perish by bacterial invasion. 
The first monads to appear are similar to those which first 
appear in the ordinary course in the feces. 
Occasionally the cysts open in the rectum of the frog, 
instead of waiting until they leave it in the feces. In this 
case the monads become parasitic for a period. Division may 
take place inside the frog under such conditions, but I have 
never seen any signs of conjugation in this situation. This is 
due, perhaps, to the inhibitory effect of the numerous other 
Protozoa which live in the frog’s intestine. Most of these 
die in the course of a day or two after removal from the frog. 
DEGENERATION. 
Even in my most healthy cultures a number of monads 
always underwent degenerative changes and died. Degenera- 
tion was also brought about by keeping the monads for many 
days in hanging-drop preparations. A want of oxygen has 
probably much to do with this, for much less degeneration 
occurs in the Schultze chambers—where oxygen is supplied 
by the presence of green algal filaments—during an equal 
length of time. 
Degenerating monads sometimes lose their regular contours, 
and become irregular and lumpy looking. Owing to the stout- 
ness of the cuticular covering they do not become ameceboid, 
as is so often the case in degenerating flagellates: Not un- 
commonly individuals grow abnormally large, being apparently 
unable to divide when they reach a certain size. These large 
and irregular forms present a very different appearance from 
that of the ordinary individuals. 
One of the first signs of degeneration is the prensa ton of 
