564 Protozoa of the Digestive and Urogenital Tracts 



eliminated and the most conspicuous feature is the macronucleus. Cysts 

 containing two ciliates have been seen occasionally, but their significance 

 is uncertain. Conjugation, but not encystment, has been observed in 

 cultures (80). 



The infection is usually localized in the colon, although invasion of 



Fig. 11. 7. A-C. Balantidium rali: A. Somewhat contracted specimen 

 from a stained preparation, showing macronncieus, several food \acuoles, 

 fibrils extending from gnllet to cortex; material apparently being dis- 

 charged from the cytopyge; x520. B. A more elongated specimen, showing 

 two contractile vacuoles and other structures; x600 (after Wenyon). C. Cyst 

 (stained preparation), bilobed macronucleus; x520. D-F. Isospora hominis: 

 oocysts with undivided zygote (D), with two sporoblasts (E), and with two 

 spores containing developing sporozoites; xl030 approx. (after May). G. 

 Trichomo7ias vaginalis, typical undulating membrane, costa, axostyle, nu- 

 cleus, parabasal body, and parabasal filament; x2400 (after Wenrich). H. 

 T. vaginalis, showing group of blepharoplasts and other structures (except 

 parabasal body); schematic (after Powell). 



