53 



Give a short- Description of Opalina. 



One of the Ciliata. It occurs as a parasite in the rectum 

 a,nd bladder of the Frog. The body is oval and uniformly 

 ciliated (Holotricha). There is no mouth and no contractile 

 vacuole. There are numerous nuclei. In summer and 

 -autumn multiplication is by fission into two, and serves 

 for increase within the host ; but in spring the process is 

 multiple fission, resulting in numbers, each containing a 

 few nuclei. These encyst and pass out from the frog into 

 the water. If one is swallowed by a tadpole, the cyst 

 wall is dissolved, setting free ciliated uninucleate bodies 

 ^the gametes) which conjugate in pairs to form zygotes 

 irorn which multinucleate Opalinas are developed. 



Write a short Note on Balantidium coli. 



Balantidium coli is a ciliate of the order Heterotricha. 

 It generally multiplies by transverse division ; but con- 

 jugation and encystment also occur. It is found in the 

 large intestine of man, in the rectum of the pig and other 

 animals. In Man it causes a form of dysentery known 

 as balantidiasis. 



What do you know about Kerona and Trichodina ? 



They are Ciliates, and they are both found upon the 

 body of Hydra, the one ( Kerona) actively creeping over 

 the cuticle and the other (Trichodina) sometimes attached 

 thereto, sometimes moving. Kerona is probably a com- 

 mensal (i.e., a harmless or beneficial associate "eating at 

 the same table "). Trichodina, which is a cylindrical 

 Vorticellid, with an adhesive disc instead of a stalk, is an 

 -ectoparasite. 



CLASS ACINETARIA. 



Describe the Acinetaria. Give an\Example. 



They are Infusorians which, in their adult state, are of 

 fixed sedentary habit and have retractile suckers or ten- 

 tacles instead of cilia. In the early or larval period of 

 their life they have cilia and are free-swimming. 



