CHAPTER XIII 

 PARASITIC CILIATES 



Ciliata are among the commonest occupants 

 -L of any small patch of stagnant water or decay- 

 ing, moist vegetation, and some of the most beautiful 

 of the Protozoa occur in this group. Many Ciliates 

 exist as free-living organisms. There are relatively 

 few parasitic forms of Ciliates known, and they are 

 not associated with any markedly deadly complaint, 

 with few exceptions. 



The body of Ciliates varies greatly in appearance. 

 Some are sessile, some stalked. There is every shade 

 of gradation between the most graceful, bell-like 

 Vorticella or Cafchesium and the flattened, leaf-like 

 degenerate Opalina, but all alike possess external 

 outgrowths of the body wall, known as cilia, by 

 which they move. Most of them also have two 

 nuclei (Fig. 49, a, b) a large one, or macronucleus, 

 which is entirely trophic in function, and a small 

 one, or micronucleus, of a totally different nature, 

 since it is concerned solely in reproduction. 



The body surface in many cases has the cilia 

 arranged in regular rows, and examination shows 

 that the vibratile threads follow the lines of con- 



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