Protozoa of the Digestive and Urogenital Tracts 547 



non is a synonym of Retortomonas Grassi. Objections to this conclusion 

 have been presented by Bishop (17). 



R. intestiymJis (Fig. 11. 2, H, I) is a small (4-9 x 3-4^) organism with 

 two unequal flagella. The longer flagellum extends anteriorly, the other 

 anterolaterally from a pit (the "oral pouch" or "cytostome"). Shape var- 

 ies somewhat although the anterior end is usually rounded. The cyto- 

 plasm often contains food vacuoles. Binary fission has been described 

 by Bishop (17). 



The cyst (Fig. 11. 2, F, G), which measures 4.5-7.0 x 3.0-4.5[j., is ovoid 



Fig. 11. 2. A-E. Tricercomonas intestinalis: flagellate stages (A, B); uni- 

 nucleate (C), binucleate (D), and tetranucleate (E) cysts; xl600 (after 

 Dobell and O'Connor). F-I Retortomonas intestinalis: flagellates from cul- 

 tures at 37° (H) and 17-20° (I); cysts (F, G); x3600 (after Bishop). J-O. 

 Chilomoastix mesnili: flagellate showing cytostomal fibril and cytostomal 

 flagellum (J), x3000 (after Geiman); late fission, new cytostomal fibrils pres- 

 ent (K), x2850 (after Geiman); uninucleate (L) and binucleate (M) cysts 

 from Macaca irus, x2850 (after Geiman); polar view of uninucleate cyst 

 from man (N), xl600 (after Kessel); binucleate cyst, nuclei joined by a 

 paradesmose (O), xl600 (after Kessel). 



