26 MANUAL OF HUMAN PROTOZOA 



nuclear membrane is delicate and a few peripheral chro- 

 matin granules are attached to it. The size, form, and loca- 

 tion of the endosome vary a great deal among different 

 individuals. In the majority, the endosome is of triangular, 

 square, or irregularly angular in shape, and may be in the 

 center, toward one side, or attached to the membrane of 

 the nucleus. In the latter case, a strand mav be seen con- 

 necting it with a smaller chromatin mass on the opposite 

 side of the nucleus. The endosome in well differentiated 

 specimens may be seen as composed of a less deeplv 

 staining matrix in which are imbedded 3-5 chromatin 

 granules. 



Cysts 



1. Living specimens. Usually ovoid in form, the cyst 

 (Fig. 5, 5) appears as a hyaline and homogeneous body 

 with a few small granules. In some there may be seen an 

 irregularly shaped vacuole which stains red brown with 

 LugoFs solution (glycogen body) which however disap- 

 pears as the cyst matures. The nuclei are rarely seen in 

 living cysts, but may be observed in Lugol-treated speci- 

 mens. The cysts measure 5-12m in diameter, the majority 

 being about 7-10|j. 



2. Stained specimens. The cyst (Fig. 5, ^^) is finely 

 reticulated. The nuclei vary in number from 1 to 4. Their 

 structure varies as in the nucleus of the trophozoite, but 

 appears to be characterized by an angular endosome and 

 its variable location within the nucleus. 



6. Dientarnoeba fragilis Jepps and Dobell 1918 



This small amoeba appears to be another inhabitant of 

 the lumen of the colon and considered as a commensal. 



