22 MANUAL OF HUMAN PROTOZOA 



ones which follow, and is an inhabitant of the lumen of 

 the colon. Like Entamoeba coli, it does not invade the 

 tissues of the colon wall and live by absorbing fluid sub- 

 stances and feeding on bacteria. Thus it is considered as a 

 commensal. This amoeba is not as common as the amoebae 

 already stated. The trophozoite and cyst are usually found 

 together in diarrhoeic faeces, while the formed faeces 

 contains cysts only. 



Trophozoites 



1. Living specimens. This amoeba (Fig. 4, l) measures 

 about 6-25m in its largest diameter, but the average indi- 

 viduals are 8-15|j. It is a fairlv active amoeba, and when 

 seen soon after being voided, it shows a monopodal pro- 

 gressive locomotion, but presently rounds itself up and 

 forms small pseudopodia, which reminds one of the slug- 

 gish amoeboid form-change of Entamoeba coll. There is no 

 sharp demarcation between the ectoplasm and endoplasm, 

 but the ectoplasm is often well recognizable in pseudo- 

 podia. The endoplasm is granulated and contains bacteria 

 in food vacuoles. Large food particles which are commonly 

 found in £. coli are ordinarily not present. The nucleus is 

 usually not distinctly seen, but the large endosome may 

 be seen surrounded by a clear circle around it in some 

 individuals. 



2. Attained specimens. The trophozoites (Fig. 4, --^) ap- 

 pear as composed of reticulated or alveolated cytoplasm, 

 depending upon the extent of degeneration (Fig. 4, 4, 5)^ 

 in which are present bacteria taken in as food material. 

 The vesicular nucleus measures about 3-4 m in diameter. The 

 endosome which is about one-half the diameter of the 



