PAEAMCECrCM. ? 



n. THE STRUCTURE OF PARAMCECIUM. 



{Paramcecium caudatum.) 



Specimens of the holotrichous infusoria will usually be 

 found in the material which has been collected to obtain 

 amoebae, and an abundant supply may be procured in the fol- 

 lowins: manner : Fill a small orlass beaker or tumbler with 

 water from one of the amoeba-aquaria described in the last 

 section. Place a small handful of pieces of hay or dead 

 moss in the water, and allow it to stand in a warm place 

 for about a week. In the winter it may be placed in the 

 direct sunlight, and even in summer the sunlight will not 

 usually be injurious. After a few days a white fihn will 

 appear upon the surface of the water ; and if the lower 

 edge of this film be carefully examined where it touches 

 the glass, great numbers of rapidly-moving white animals, 

 so small as to be barely visible without a lens, will 

 usually be found. When examined with the microscope 

 many or most of these organisms will be found in nearly 

 every case to belong to the species which is here described, 

 but even if this species is not found, almost all the points 

 of the description may be verified in any of the holotrichous 

 infusoria. 



Transfer a drop from the surface of the water to a glass 

 slide by means of a dropping-tube, in the way which has 

 been described in Section I. Cover it with a thin glass 

 supported by a small piece of paper or a hair, and examine 

 it with a magnifying power of eighty or one hundred 

 diameters, and notice the oval animals gliding actively 

 across the field of view. Find one whose motions are 

 somewhat restricted by the cover, and, after placing it as 



