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Information on Infusoria and Light Microscopy.
Infusoria and Light Microscopy
The Infusoria group contains many of the microscopic objects familiar to us from high school study of biology, such as Vorticella, Stentor and Paramecium. The group derives its name from the fact that many of the individ- uals were first discovered in infusions, that is, water in which animal or vegetable matter had been steeped and was decaying. Since their first discovery the animals have been found in great variety and abundance in even the sweetest water, although they abound in incredible numbers in stagnant pools. The best way to procure specimens is to place the dip- net under the mass of aquatic plants upon which they are found and lift the mass with the net. If the plant is lifted from the water, the water draining away will carry with it many of the specimens, which are thus lost. A bottle may be placed under the plant and the leaves and stems scraped with the bottle rim, when the Infusoria will be carried into the bottle. Some of them are free-swimming, others are permanently attached to water plants, while a third group builds shells like those of the rhizopods. The free-swimming varieties may be easily collected and placed upon the slide for examination, while those per- manently attached may be found only by cutting away a part of the plant and examining it. Some of the most interesting types are firmly adherent to the water plant Utricularia and to other plants with finely divided leaves, every part of which should be searched with the micro- scope, especially the forks of the leaves. Those that build cases secrete a sticky substance to which extraneous floating matter is pretty sure to ad- here, building up a protective covering which surrounds the animal. These cases or loricae are built of material carried toward the animal by motion set up in the water by organs with which it is provided. These organs serve to create a current of water which carries food to the animal, for being immobile it cannot move about in search of food. One very beautiful form of Infusorium representing the fixed type is the species of Carchesium, illustrated in Fig. 28. The single stem, which is attached to some submerged object, divides at the summit into a large number of branches, each one bearing at its end a tiny bell-shaped Infusorium, while numerous other individu- als are disposed along the stems on branchlets of their Own. Many of the fixed Infusoria are equipped with muscles that enable them to contract when alarmed, of which Carchesium is a good example. Running through the stem and all of the branches is a cord-like muscular thread which contracts when the animal is stimulated, pulling the entire colony, which is colorless and may con- tain as many as a hundred individuals, toward the point of attachment. This contractile property is elective, for one branch at a time may be affected without disturb- ing the others, or the entire colony may contract at once. All Infusoria are provided with cilia (hairs) or flagella (lash or thread-like appendages) , which serve two purposes. They provide a means of locomotion, and by their vibration create a current of water which moves food par- ticles toward the animal. Carchesium is an example of the ciliated type in which the front or large end of the bell is surrounded by a wreath of cilia visible under a high power. When the creature contracts these vibratile hairs fold together and the animal appears like a tiny ball.
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Microscope Slides 
