33f, 



THE AMERICAN NATURALIST 



[Vol. LIV 



H. Body drawn out bluntly po 

 riorly, obliquely truncated 

 teriorly 



EH. Body drawn out into an ac 

 nate tip posteriorly, not 1 



.Cercobodo 



'. Flagella more than 2. 

 D. Flagella 3, two trailing, one extended forward . .ElvirecP- 



produced into 2 filamentous appendages. 



In dealing with these minute, free-swimming forms, it 

 was of first necessity to devise some means of keeping 

 them quiet and within the field of the microscope when 



of retarding movement and of killing were used, but 

 those which gave the best results were the following. 



For the first examination of any sample,, a small drop 

 of the culture was taken and mixed on a slide with a drop 

 of very viscous gelatine solution, 2 and the whole thor- 

 oughly stirred together. Or often several drops of the 

 culture were mixed with an equal part of the gelatine 

 solution in a watch crystal and used on the slide when 

 needed. Such a preparation would not keep the pro- 

 tozoa confined within it alive for more than half an hour, 

 however, due to the occlusion of the necessary oxygen. 



The drop on the slide was now carefully flattened out 

 and examined without a cover glass under a low power 

 (16 mm. objective and lOx eyepiece) to ascertain whether 

 the solution were of a viscosity great enough to check 

 sufficiently the movements of the flagellates. If not, it 

 was allowed to concentrate still more by evaporation 

 until properly viscous, and then covered with a cover 

 glass. Magnification with the 4 mm. objective and the 

 8x and lOx eyepieces was found to be great enough for 

 the identification of most of the forms. 

 , The gelatine used in this method must be of the best 

 grade and perfectly fresh and clear. It may be slightly 



the higher powers were in 



Several methods both 



