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GUIDE TO THE STUDY 



Balantidium coli, a cause of dysentery in man, is also commonly 

 found in pigs. If living specimens are available, note the dis- 

 tribution and the action of the two types of cilia. The peri- 

 stome is a slitlike depression at the anterior end leading into the 

 mouth, or cytostome. In the living specimen two contractile 

 vacuoles may be seen, in addition to numerous food vacuoles. 



Fig. 31. — The life history of Opalina ranarum, after Neresheimer. A, multi- 

 nucleate stage; B, oblique fission as it occurs in summer, fall and winter; C, 

 gametocytes produced by repeated divisions in the springtime, encyst, are taken 

 up by tadpoles and produce, D, gametes which copulate and form cysts from 

 which escape; E, the uninucleate infusorian which develops into A. 



At the posterior end is the anus, or cytopyge. There is a bean- 

 shaped macronucleus and a rounded micronucleus. 



Reproduction is by transverse fission and also by conjugation 

 and cyst formation. Search your preparation for the large 

 spherical cysts with a thick outer wall. Examine demonstration 

 sections of the large intestine showing balantidia in situ. 



References 



McDonald, J. D., 1922. On Balantidium coli (Malmsten) and Balantidium 

 suis (sp. nov.) with an account of their neuromotor apparatus. Univ. 

 Calif. Pub. Zoology, 20 : 243-300. 



Metcalf, M., 1923. The opalinid ciliate infusorians. U. S. Nat. Museum 

 Bull. 120, 484 pp. (Extensive bibliography.) 



