BALANTIDIUM COLI 



121 



.anterior end is there broadest and becomes narrower as it obliquely approaches 

 more or less towards the posterior extremity ; there are coarse cilia along 

 the entire left border and the front part of the right border ; longitudinal 

 striation distinct and regular ; there are two contractile vacuoles to the 

 right, and occasionally also two or more to the left. The anus has a 

 terminal position. Macronucleus oval or horse-shoe shaped, micronucleus 

 contiguous. The movement is always darting. The cysts are globular 

 or oval. Parasitic in the terminal gut of human beings and pigs, in 

 amphibians and in the body cavity of polychaetic annelida. 



i. Balantidium coli (Malmst.), 1857. 

 Syn. Paramcecium coli, Malmsten, 1857. 



Body oval, 0*06-0- 1 mm. in length (up to 0*2 mm. according 

 to Janowski), and 0-05-0-07 mm. in breadth. The peristome is 

 funnel-shaped or contracted, the anterior end being, accordingly, 

 either broadened or pointed. The ecto- and endo- sarc are distinctly 



FIG. 62. Balan- 

 iidium coli. (a) 

 Nucleus ; (b) vacu- 

 ole ; (c) peristom 

 (d) bolus of food 

 (after Leuckart). 



1 



5B 



a. b. 



FIG. 63. Balantidium coli, free and en- 

 cysted ; (a) anus ; (n) nucleus ; (b) bolus of 

 food (after Casagrandi and Barbagallo). 



separate, the latter granular, and containing drops of fat and 

 mucus, granules of starch, bacteria, and occasionally also red and 

 white blood corpuscles ; there are usually two contractile vacuoles, 

 sometimes even more. The anus opens at the posterior extremity. 

 The macronucleus is bean- or kidney- shaped, rarely oval ; the micro- 

 nucleus globular. 



It lives in the large intestine of man and in the rectum of the 

 domestic pig ; it propagates by transverse division, but conjuga- 



