26 STRUCTURAL AND SYSTEMATIC ZOOLOGY 



amcebalike changes in the shape of the body, and by 

 the presence of a whiplashlike organ (flagellum) by 

 means of which it propels itself through the water. 



Topics for Study. The elongated, highly flexible 

 body, its motions and color; the position and move- 

 ments of the flagellum; the red stigma, or "eye spot," 

 and the contractile vacuole, both near the mouth 



(Fig. 4). 



Paramecium 



Material. The slipper animalcule is more readily 

 obtained than almost any other of the protozoa. There 

 are various ways of raising it in abundance for labora- 

 tory purposes. Hay or marsh grass cut into pieces a 

 few inches long may be placed in a convenient dish, 

 covered with water, and set in a warm room for one or 

 two weeks, at the end of which time there will probably 

 have formed a pellicle on the surface. This will con- 

 sist largely of rod-shaped or threadlike bacteria, and 

 feeding upon them will be seen many kinds of infusoria, 

 among the latter being Stylonychia, which may be recog- 

 nized by its large bristlelike cilia and its springing 

 motions, and Paramecium, the "slipper animal," covered 

 everywhere with fine cilia and having a more smooth, 

 gliding movement. Another satisfactory method of 

 procuring specimens is to place a handful of water 

 plants, like Anacharis (waterweed), Utricidaria (bladder- 

 wort), or Potamogeton (pond weed) in just enough water 

 to cover the plants, and let the mass stand in a warm, 

 dark place until decay begins, at which time the water 

 will probably be found to be swarming with animalcules. 



In preparing the specimens for microscopic examina- 

 tion, follow the directions given for amoeba. It is 

 always well to put under the cover glass a few frag- 

 ments of the scum consisting of bacteria, for the ani- 

 malcules will gather around these masses and remain, 



