354 OHIO BIOLOGICAL SURVEY 



water supplies are obtained, quantitative methods of study must be 

 used. A measured amount of water— 500-2000cc— is passed 

 through an apparatus for concentrating the organisms. This may 

 consist of a glass funnel inserted into the stoppered neck of a 

 wide mouth bottle holding about 250cc and which also has as an 

 overflow, a glass tube with a piece of '"bolting cloth" covering the 

 inner end. The organisms may be reconcentrated after reaching 

 the laboratory by passing through a funnel having some fine quartz 

 sand in the bottom of the funnel supported by a cork with a piece 

 of ''bolting cloth" holding the sand in place. The sand must not be 

 allowed to dry but be washed out in a watch glass in distilled water, 

 the distillation of which has been accomplished in glass vessels 

 with due care. 



After having obtained material, rough observations made in 

 the laboratory by placing a small quantity of water in a watch 

 glass and examining with a magnification of 60-150 diameters, will 

 give an idea as to the various genera and species represented. In 

 order to properly classify the species, however, one must take a 

 clean slide and cover glass and study with magnifications of from 

 500-2500 diameters, as well as ascertain the dimensions of the par- 

 ticular organisms with either the ocular micrometer or the camera 

 lucida, the magnification of the microscope having first 

 been obtained with the stage micrometer. In this connection it 

 will be advisable to consult some of the introductory books in 

 microscopy, such as that of Gage (Comstock Publishing Company, 

 Ithaca, N. Y. Price $2.00) if one has not previously had experi- 

 ence. 



The method which the writer has found best adapted for 

 studying the Euglenoids and other microscopic organisms in the 

 living conditions is that of utilizing a lens-paper aquarium. A piece 

 of lens-paper is cut with the dimensions smaller than the cover 

 glass, then by trimming out the center a ring-lie piece is left. 

 This is placed on the middle of the slide and attached by a drop 

 of water from a pipette. Then a drop of water containing the 

 organisms is placed in the center, and a cover glass carefully placed 

 over it, avoiding air bubbles by lowering gently with the tweezers. 

 Immediately tilt the slide and draw off any surplus water with 

 the pipette. The aquarium will keep for several hours and the 

 cover glass will be supported by the thin layer of lens-paper and 



