264 C. CLIFFORD DOBELL, 
quite motionless inside the spores, When the latter are 
fully formed the oocyst usually collapses over them (fig, 91), 
so that they remain loosely encapsuled together. Sometimes 
the oocyst completely breaks up if kept in a liquid medium, 
and the spores then become free. They measure ca. 14 by 
7. Their resemblance to the spores of Monocystis is 
often very striking in early stages of development. As I 
have already noted (p. 206), these spores are not uncommon 
in frogs. Of course, when fully formed the octozoic Mono- 
cystis spores cannot possibly be mistaken for the dizoic 
spores of the Himeria. 
As in all the other forms investigated, I have found great 
difficulty in causing the contents to emerge, The gastric juice 
of the frog is quite without action upon the spores. So also 
are 2 per cent. HCl, 3 per cent. Na, Cos, and artificial solutions 
of trypsin or pepsin, The juices from the small intestine of 
laboratory frogs is also, as a rule, without effect. On a single 
occasion, however, when I used the juice from the upper part 
of the small intestine of a frog killed almost immediately after 
it was captured, I saw the following events take place: In 
three or four spores lying near to one another, the sporozoites 
—after about a quarter of an hour—began to move about 
inside their spores. The movements increased, and finally 
the sporozoites were seen in a state of great activity, chasing 
one another round and round inside their narrow prison, 
jostling the residual mass. After this had continued for 
another hour one spore suddenly burst and a sporozoite 
emerged. But it then, almost at once, ceased to move, and, 
after swelling up, died and broke into fragments. The other 
sporozoites all became motionless subsequently, and none of 
them came out of their spores. All other attempts to get 
them to emerge have been fruitless. 
I think this experiment indicates that the spores are pro- 
bably dissolved, and the sporozoites emerge, in the upper 
part of the small intestine of the frog. The reason that 
experiments are nearly always negative is probably to be 
sought in the changes which the digestive juices undergo in 
