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MANUAL OF ELEMENTARY ZOOLOGY 



The Ciliata are not commonly parasites of man, but 

 one at least may cause in him serious disease. 

 co| l L l,t "" l,m Balantidium coli is related to Paramecium. It 

 has an egg-like body, about one-tenth of a 

 millimetre in length, with a funnel-like depression — the 

 peristome — at the narrow end, and a mouth and gullet at 

 the bottom of the peristome. A coat of cilia arranged in 

 parallel rows covers the body, and some larger cilia stand 

 beside the peristome. There is a good-sized, kidney- 

 shaped meganucleus, with a small, round micronucleus 



against its hollow side, and 

 two contractile vacuoles. Red 

 blood corpuscles are sometimes 

 found in the food vacuoles. 

 The animal multiplies by trans- 

 verse, binary fission, and from 

 time to time conjugates. In 

 meg. certain circumstances it encysts. 

 It lives in the large intestine 

 of the pig, to which it appears 

 not to do much harm, and is 

 spread by its cysts passing out 

 with the fasces, getting into 

 water or on to food, and being 

 swallowed by a new host. 

 When this is a human being 

 whose intestine is deranged, it 

 increases the irritation, pene- 

 trates the epithelium and lies 

 in the layers below it, and 

 may even be carried by the blood or lymph to other 

 parts of the body and there cause abscesses. More often 

 it brings about dysentery, which may be fatal. It occurs in 

 all parts of the world. A Balantidium is found, with other 

 ciliates, in the rectum of the frog. 



Fig. 98. — Balantidium coli. 



c.v., Contractile vacuoles; f.v., food 

 vacuole ; £-., gullet ; meg-., mega- 

 nucleus ; mi., micronucleus ; v.. 

 vestibule or peristome. 



The rectum of the frog contains an interesting population of ciliates 

 niiiott. nt ^ hich Iive chieflv in the 1'ghter-coloured contents of its 



the Frog. foremost region. Balantidium entozoon differs from B. 



coli in having four contractile vacuoles and a longer peri- 

 stome. Nyctotherus cordiformis resembles the Balantidia in its general 

 features, but is bean-shaped, with a long gullet placed in the middle of 



