PROTOZOA IN THE DIGESTIVE TRACT 51 



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Fig. 13. Balantidium coli. x 530. (original) 



1. A lix'ing trophozoite. 



2. A stained trophozoite. 



3. A fresh cyst. 



4. A stained cyst, 



ous. The micronucleus may also be seen. Food particles 

 of different kinds are stained in different tones. 



Cysts 



1. Living specimens. The cysts (Fig. 13, ^) are rounded 

 or ovoid and appear slightly yellowish or greenish in 

 color. They are about 40-60n in diameter. The wall is 

 composed of two membranes. In a newly formed cyst, 

 the ciliate may be seen actively revohing inside the wall, 

 with the posterior contractile vacuole contracting rh\ thmi- 



