PHYLUM PROTOZOA 



Class : Infusoria 

 PARAMECIUM 



Paramecium, often called the slipper animalcule, is one of the 

 commonest of the larger infusorians. It is a minute, single-celled 

 animal, being just on the limit of vision, and is often present in 

 standing water which contains decaying vegetable matter. It 

 may usually be obtained by permitting vegetable matter from a 

 pond to stand in water for a week or two. In shape it is an elon- 

 gated ellipsoid with a wide, slightly twisted, longitudinal groove, 

 called the oral groove, on one side ; the surface which contains 

 the groove may be called the ventral surface, and the opposite 

 surface, the dorsal. The animal is colorless and transparent, ex- 

 cept when it contains within its body colored food particles. 



Mount a drop of water containing Paramecia and some decay- 

 ing matter together with a few strands of cotton on a slide, using 

 a large, thick cover glass, and study the animals under a low 

 power of the microscope. They will be seen swimming rapidly 

 about, but will gradually collect around the decaying matter or 

 be entangled in the cotton. If they do not become quiet in a 

 few minutes, it is because there is too much water under the 

 cover glass, and some of it should be withdrawn with a piece of 

 blotting paper. Care should be taken that the water does not 

 entirely evaporate. 



Observe the unsymmetrical shape of the animal, and the dif- 

 ference between the anterior and the posterior ends. Notice the 

 rolling over of the animal as it swims through the water; the 

 peculiar spiral twist of the body is correlated with this motion, 

 but does not necessarily cause it, since the animal may at times 

 revolve in the direction opposite to that of the twist. It is in con- 

 sequence of this peculiar revolving motion that the animal is able 



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