CHAPTER X 



PROTOZOA 

 INFUSORIA 



A CILIATE INFUSORIAN. A FREE-SWIMMING CILIATE (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 almost 

 universally present in standing water which contains decaying 

 vegetable matter. It is easily obtained by permitting vegetable 

 matter to stand in water for a week or two. In shape it is an 

 elongated ellipsoid with a wide, slightly twisted, longitudinal 

 groove, called the oral groove, on one side ; the surface which con- 

 tains the groove may be called the ventral surface, and the oppo- 

 site surface, the dorsal. The animal is colorless and transparent, 

 except when it contains within its body colored food particles. 



Mount a drop of water containing Paramecia and some decay- 

 ing matter 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 about 

 the decaying matter. 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 glass, and some of it should be withdrawn with a piece of 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 

 all evaporate. 



Observe the unsyrnmetrical shape of the animal, and the 

 difference between the anterior and the posterior ends. Notice 

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



164 



