THE INTESTINAL PROTOZOA OF FROGS AND TOADS. 253 
When the cysts reach this stage they cease to develop. I 
have never found cysts containing more than four nuclei. 
The cysts remain in this condition for many days if left in 
water. If dried they invariably die. But even in the water a 
large proportion of cysts always degenerated, gradually 
breaking up (fig. 78). 
Attempts to cause the cysts to develop further in the 
intestinal juices of frogs have always been negative—as I 
believe, owing to the abnormal state of the frogs used (cf. 
pp. 2138, 264). 
If we compare the nucleus of the smallest kind of amceba 
found in the frog (fig. 54) with the nuclei in the fully-formed 
cyst (fig. 77) we cannot fail to be struck by their similarity. 
‘hey correspond closely in structure and size. It appears to 
me probable that when the cyst reaches its new host’s gut 
its contents break up into four small amcebe, which are then 
set free and grow up into the ordinary form, just as in 
Hntameceba coli the cysts hberate broods of eight (Schau- 
dinn [{43]). 
Perhaps it may also be inferred, from the kind cf chro- 
matin reduction which takes place during encystment, that the 
four nuclei are reduced gamete nuclei, and the small amcebze 
liberated from the cysts conjugate with one another, But 
this is mere hypothesis. The history of the chromatin is, at 
all events, suggestive. 
Now it must be apparent to anyone reading this descrip- 
tion and looking at the figures that at certain stages of 
development there is an extraordinary resemblance to certain 
stages in the autogamy of H. coli (Schaudinn [48]) and EH. 
muris (Wenyon [87]). Indeed, had one encountered isolated 
stages, and had one not been able to follow up every stage of 
development, one would be strongly inclined to believe that 
an autogamy occurred also in H. ranarum. (Compare 
some of the figures in Pl. 4 with those of Wenyon, e. g. the 
cyst with two spindles [fig. 72], with a similar cyst [fig. 23, 
Pl. 10] of Wenyon’s paper). I do not for a moment suggest 
that Schaudinn and Wenyon were guilty of misinterpreting 
