OPALINA 7 



this union certain changes occur in the nuclei 

 and paranuclei of both individuals, resulting in 

 the so-called 'rejuvenescence of the nuclei,' and 

 followed by rapid and repeated fission of the two 

 Paramecia. 



Ill OPALINA 



Opalina is a protozoon usually found hving in large 

 numbers in the large intestine of the frog. From its large 

 size and the ease and certainty with which it can be obtained 

 it is a very convenient form for examination. 



Slit v/p the large intestine of a freshly -fithed frog ; scrape 

 away the contents together with the mucous membrane of the 

 intestine, and dilute with salt solution ('75 per cent.). 

 Examine a drop of the mixture microscopically. 



A. General appearance. 



Opalina is a flattened, asymmetrically oval body, about 

 ■^ inch long, covered with cilia by means of which it swims 

 actively. It has neither mouth nor anus. 



B. Structure. 



1. The ectosarc is thinner than in Paramecium. There 



are no pulsating vacuoles, and no trichocysts. 



a. The cuticle, if present at all, is exceedingly thin. 



b. The cilia are of equal size over the whole surface. 

 e. ' Myophan' striations are obvious : they are mainly 



longitudinal. 



2. The endosarc contains no food- vacuoles, owing to the 



fluid nature of the food : this also accounts for the 

 absence of a mouth, the nutriment being absorbed 

 by the whole surface of the cell-body. 



a. The nuclei are numerous. 



C. Beproduotion. 



This is effected by oblique or transverse fission 



