300 
Entamoeba histolytica and E. ranarum 
others, but apart from this the results of the examination of subcultures 
Ao, A 3 , B. 2 , B 3 , B it and C 2 were closely similar. As culture B 3 was 
followed for the longest period, I will give the results of the examinations 
made upon these tadpoles as an illustration of the findings in general. 
(The differences observed in other cultures will then be briefly indicated.) 
Subculture B 3 . 
Eggs fertilized March 16, 1916. 
Tadpoles fed on human faeces containing immense number of ripe 
E. histolytica cysts, March 24. 
Tadpoles killed and examined on following dates: 
March 26. Gut-contents of tadpoles contain a very large number 
of apparently quite healthy and unchanged E. histolytica cysts. No 
amoebae or other free organisms. 
March 27. The same; but some dead cysts also found. 
Same as preceding. 
The same, but dead cysts rather more plentiful. 
April 2. Many cysts still present, but the majority dead. 
,, 5. Fewer cysts, mostly dead. 
A very few cysts found with difficulty; all appear dead. 
No cysts or free organisms discoverable in gut-contents. 
Same as April 21. 
28. 
29. 
2 
May 
16. 
21 . 
27. 
3. 
11 . 
12 . 
13. 
It will be evident from the foregoing that living cysts, but no 
amoebae, were found in the tadpoles fed on infected human faeces until 
the 12th day after the first feed. During this time the proportion of 
dead cysts gradually increased. On the 23rd day only a very few 
dead cysts were found; and thereafter, until the 50th day, none. 
The other five subcultures mentioned above gave similar results, only 
differing in the dates at which cysts (all dead) were last found in the gut- 
contents. These dates were as follows: 
^2 
^3 
B , 
0 2 
Cysts last seen on 23rd day 
yy yy 
yy yy 
20th 
6th 
yy 
yy 
yy yy 
yy yy 
yy 
yy 
19th 
9th 
