24 MANUAL OF HUMAN PROTOZOA 



in form, which is a characteristic feature of this amoeba 

 (Fig. 4, 6). Naturally the cysts vary a great deal in dimen- 

 sions. More or less rounded cysts measure usually 6-15^ 

 in diameter. The contents appear hyaline, but there is a 

 conspicuous clear sharply outlined body which stains 

 reddish brown with Lugol's solution and is considered as 

 a glycogen body. It may be one-third to one-half the 

 diameter of the cyst. Because of the presence of this glyco- 

 gen body, the cysts had formerly been called "I cysts," 

 before their relation to the trophozoite became known. 

 Unlike the glycogen body present in the cysts of other 

 amoebae already described, it persists in the majority of 

 cysts in the present species, although it may become 

 smaller when the cysts are kept in the faeces for several 

 days. The nucleus is ordinarily faintly seen in a living 

 cyst, but when treated with Lugol's solution, it may be 

 recognized more clearly because of the characteristic 

 endosome. 



2. Stained specimens. The contents of the cyst (Fig. 4, 

 7-10) are reticulated and one (sometimes two) large clear 

 vacuole is invariably noticed, which is the glycogen vacu- 

 ole. The nucleus is usually situated close to the vacuole 

 at one point. The endosome is often attached to the nuclear 

 membrane and may be crescentic in shape. There is a 

 single nucleus. Binucleate cysts are of rare occurrence and 

 considered to be abnormal forms. 



5. Endolunax nana (Wenyon and O'Connor 1917) 



This is one of the two smallest amoebae living in man 

 and inhabits the lumen of the colon. It has not been seen 

 to invade colon tissues and is therefore considered as a 



