38 GENERAL HISTORY OF 



very minute mechanical division. The bodies generally 

 used are those of carmine, indigo, and sap-green, the first 

 being preferable. This material should be as pure as 

 possible. Take a piece or cake of it, and rub the corner 

 once or twice on the stage-glass, or what perhaps is better, 

 the lower plate of an aquatic live-box, having first moist- 

 ened it with a drop of water. The colouring requisite 

 for the purpose is very small — only just sufficient to 

 render it appreciable to the naked eye — for if there be 

 too much, the probability is, that the particles will be too 

 large for the creatures to imbibe. Having thus prepared 

 the coloured food, place a drop of it beside a drop of the 

 water containing the animalcules, but not so that they 

 may come into contact ; then put on gently the cover of 

 the live-box, and lower it sufficiently to flatten the two 

 drops of fluid, but not to force them to unite. Now 

 place the live-box under the microscope, and examine the 

 animalcules as closely as you can, and especially so as to 

 ascertain that their stomachs are colourless; then press 

 down the cover until the drops of fluid intermix, which 

 may be done under the microscope, and you will imme- 

 diately perceive the creatures in great activity, and readily 

 distinguish the cilia, proboscides, and other organs, of those 

 which possess them, and in a few seconds their stomachs 

 will be filled with the coloured substance. Some animal- 

 cules, however, take a considerable time to effect this, but 

 it is an exception to the general rule. 



