178 ANARTHROPODA 



14. PROTOZOA: ONE-CELLED MICROSCOPIC ANIMALS 



The members of this phylum are single-celled animals, 

 and so small that but few of them can be seen with the 

 naked eye, and some are so minute as to be visible only 

 under the highest powers of the microscope. They abound 

 in the dust of the air, in the surface layers of the earth, 

 and in the water, while many parasitic forms make their 

 homes in the living bodies of the higher animals and plants, 

 sometimes causing disease. 



Slipper Animalcule (Paramoecium). This is a repre- 

 sentative of the class Infusoria, which includes most of the 



protozoa commonly pres- 

 ent in infusions made by 

 soaking grass, leaves, or 

 flowers in water. Para- 

 moecia may usually be se- 

 cured by placing a bunch 



FIG. 208. Slipper animalcule showing t i <,,. i^ fl plioV, n f 



the nucleus, a dark circle, and the 



buccai groove on the lower side. En- stagnant water f or a week 



larged two hundred diameters. 



or two. 



For study, a small drop of water containing a number 

 of specimens should be transferred to a glass slip, and one 

 or two minute threadlike green plants added to the drop 

 before the cover glass is placed thereon. Having seen with 

 the low power that the animals wanted are present in the 

 mount, absorb with blotting paper the superfluous water 

 about the edge of the cover glass, drop near its margin a 

 half dozen pieces of paraffin, and with a red-hot nail 

 held in a cork melt the paraffin so it runs slightly over the 



