22 CILIATA. 



abundance in the diphtheritic growths in fowls, but the exact 

 part it plays in the disease is not known. Another species 

 is found in the liver of pigeons. 



The Ciliaia have a more complicated body than the forms 

 we have been considering. They may have a definite mouth 

 and anus, and have not only a nucleus but a distinct para- 

 nucleus. Some forms, such as Vorticella, the bell-animalcule, 

 are stalked. They are all more or less covered with fine 

 vlbratile cilia. Eeproduction takes place by a process of 

 budding or "gemmation." This gemmation is when one of 

 the divided parts of the ciliate is smaller than the other : the 

 smaller part — the bud — breaks off, then floats away and forms a 

 fresh specimen. Eeproduction also takes place by direct fission, 

 whilst conjugation is of common occurrence, the conjugating 

 individuals usually being of different sizes. 



The Ciliata are divided into four groups, as follows : — 



(All the cilia alike and 

 short . . ■ (i) Holotriclue. 

 A row of long cilia 

 around the mouth . (ii) Hcterotrichce. 



B. Cilia on ventral surface (iii) Hypotrichce. 



C. Cilia arranged in a crown around the mouth, and 



often in the form of a girdle .... (iv) Peritricha. 



The Holo-, Hetero-, and Peritrichae are all found in domestic 

 animals. Two holotrichse, known as Isotricha prostoma and /. 

 intestinalis, are abundant in the rumen of ruminants. They 

 are not there as parasites but as commensals. Commensalism 

 is when an animal lives upon another animal, occasioning not 

 only no harm but actually benefiting its host. 



On the other hand, a species called Glohidium Leuekarti 

 causes serious inflammation of the mucous membrane of the 

 horse's intestine. A very deadly disease in horses and mules 

 in India, called surra, is due to one of these infusoria, Trypano- 

 soma Evansi, which takes up its abode in the blood, producing 

 a pernicious anaemia. Whilst the infusoria increase there is also 



