Protozoa of the Digestive and Urogenital Tracts 553 



eccentric endosome measuring a third to half the nuclear diameter. 

 Nuclear granules may be scattered on a "network" or may lie just within 

 the membrane. The nucleus has been described by Wenrich (167). Pre- 

 cystic stages are rounded amoebae without food vacuoles and either with 

 or without glycogen. 



The cyst (Fig. 11. 4, K-N), usually more common than the trophozoite 

 in stool samples, measures 6-16[x and is nearly always uninucleate. For 

 example, only 0.2 per cent of the cysts were binucleate in one series of 

 examinations (159). The cyst may be spherical but is more often irregular. 

 Inclusions resembling chromatoid bodies of other amoebae have been 

 seen occasionally (167), but a large mass of glycogen is characteristic. 



Dientamoeba fragilis 



Jepps and Dobell 



In this amoeba the percentage of binucleate forms has ranged 

 from 9.0 (168) to about 80 (81) in different infections. Occasional speci- 

 mens contain more than two nuclei (49), sometimes as many as seven 

 (173). Several detailed descriptions have been published (81, 166, 168, 



^<./ :^ 



'-^..-.iili--^' 



Fig. 11. 5. Dientamoeba fragilis, xl600 (after Wenrich). A. Uninucleate 

 form, interphase nucleus. B. A single prophase nucleus with four chro- 

 mosomes. C. Feulgen preparation, single nucleus with eight chromosomes. 

 D. Single nucleus in anaphase. E. Early telophase, with paradesmose. F. 

 Binucleate form with persisting paradesmose. G. Two nuclei in interphase. 



169), and the most recent descriptions of nuclear division are those of 

 Dobell (49) and Wenrich (172). The literature has been reviewed by 

 Wenrich (173). 



The diameters of rounded amoebae range from 3.5 to about 20tj,. Move- 

 ment is active, with broad and usually clear pseudopodia. A number of 

 food vacuoles may be present. The nucleus (Fig. 11. 5) usually shows a 

 central group of 4-8 granules, four being the most common number. In 

 mitosis, the division of four chromosomes into eight has been demon- 

 strated (169, 172) and the central group of granules represents these 

 chromosomes. A reticular organization of the nucleus also has been ob- 



