CHAPTER V 

 PARAMECIUM 



(Paramecium caudatum Ehrbg.) 



Paramecium, like Ameba, is a unicellular organism, but is 

 further advanced in the scale of life. It also is found in fresh 

 water ponds and streams, and is very easily obtained. Cultures 

 prepared for Ameba will in most cases sooner or later contain a 

 host of Paramecia. 



General Anatomy. If a drop of water containing Paramecia 

 is placed on a slide, the animals may be seen with the naked eye 

 moving rapidly from place to place. Under the microscope they 

 appear cigar-shaped (Fig. 23). A closer view reveals a depression 

 (o.g.) extending from the end directed forward in swimming, 

 obliquely backward and toward the right, ending just posterior 

 to the middle of the animal. This is the so-called oral groove or 

 peristome. The mouth (m.) is situated near the end of the oral 

 groove. It opens into a funnel-shaped depression called the 

 cy to pharynx or gullet (g.), which passes obliquely downward and 

 posteriorly into the endosarc (en.). The oral groove gives the 

 animal an unsymmetrical appearance. Since Paramecium swims 

 with the slender but blunt end foremost, we are able to distinguish 

 this as the anterior end. The opposite end, which is thicker but 

 more pointed, represents the posterior end, while the side contain- 

 ing the oral groove may be designated as oral or ventral, the oppo- 

 site side aboral or dorsal. The motile organs are fine threadlike 

 cilia regularly arranged over the surface. Two layers of cyto- 

 plasm are visible, as in Ameba, an outer comparatively thin clear 

 area, the ectosarc (ec.) and a central granular mass, the endosarc 

 (en.). Besides these a distinct pellicle (p.) or cuticle is present 



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