FOR THE MICROSCOPE. 97 



and vice versd ; thus, tlie required specimens may be taken out 

 singly with one of the tubes, and phiced in the aquatic live-box 

 for --observation. The observer will derive much assistance in this 

 operation li'om the use of the pocket-magnifier before mentioned, or 

 fi*om a watchmaker's eye-glass and stand. 



When the Infusoria are extremely minute, they usiially congregate 

 at the edge of the water over the white portion of the cardboard, 

 and may be removed from thence with the point of a quill, or of a 

 small wedgcd-shaped pencil. If a quantity of the Chara, or other 

 aquatic plants, be put into a glass jar -nath the Infusoria, in the 

 course of a few days, more or less depending upon the temperature 

 of the season, the surface wiU be covered with a thin pellicle, formed 

 by the decomposition and extrication of gas, causing the small 

 detached pieces of vegetable matter to float upon the water, and 

 with them the Infusoria. Let a small portion of this film be taken 

 fi-om the siu-facc, by means of the feeding pin, drawn in the 

 margm, and examined under the microscope, and you will 

 hardly fail of being highly gratified. Among the most 

 interesting genera collected fi-om the surface of these infu- 

 sions, in the manner just stated, are those belonging to the 

 families Vorticellina, Arcellina, and Astasicea. After the 

 film has remained some days upon the water, many of the 

 above-mentioned genera disappear, and are succeeded by 

 those of the family Vihrionia, especially the Bacterium. 

 These, however, may be easily overlooked ; for they merely 

 resemble, even under a power of 250 diameters, siiitillations, 

 or the vibrations of cUia, among the vegetable matter. But 

 when carefully examined rmder a higher power, they will appear 

 like so many small short jointed rods, each rod, or chain, having a 

 distinct movement of its own. 



When it is desu'able to keep li\'ing Infusoria, it is necessary to 

 examine the vessels in which they are, every day or two, to ascer- 

 tain whether they contain any Entomostracea, or larvse of insects, as 

 they feed upon the animalcules, and thus your choice specimens will 

 be desti'oyed. From time to time, as these appear, remove them. 

 It may happen that, at first, the water may not contain them, but 

 only their eggs, which, in a few days, may be hatched, and the young 



