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Chapter 45 

 Collection, Cultivation, and Observation of Protozoa 



Collection 



N THE foregoing chapters it has been pointed out that various 



species of Protozoa have characteristic habitats and that many 

 of free-living forms are widely distributed in bodies of water: fresh, 

 brackish, and salt; while the parasitic forms are confined to specific 

 host animals. Of free-living Protozoa many species may occur in 

 large numbers within a small area under favorable conditions, but 

 the majority are present in comparatively small numbers. If one who 

 has become acquainted with the representative forms, intends to 

 make collection, it is well to carry a compound microscope in order 

 to avoid bringing back numerous jars containing much water, but 

 few organisms. Submerged plants, decaying leaves, surface scum, 

 ooze, etc., should be examined under the microscope. When desired 

 forms are found, they should be collected together with a quantity of 

 water in which they occur. 



When the material is brought into the laboratory, it is often nec- 

 essary to concentrate the organisms in a relatively small volume 

 of water. For this purpose the water may partly be filtered rapidly 

 through a fine milling cloth and the residue quickly poured back 

 into a suitable container before filtration is completed. The container 

 should be placed in a cool moderately lighted room to allow the or- 

 ganisms to become established in the new environment. Stigma- 

 bearing Phytomastigina will then be collected in a few hours on the 

 side of the container, facing the strongest light, and the members of 

 Sarcodina will be found among the debris on the bottom. Many 

 forms will not only livejong, but also multiply in such a container. 



For obtaining large freshwater amoebae, fill several finger bowls 

 with the collected material and water, and place one or two rice 

 grains to each. After a few days, examine the bottom surface of the 

 bowls under a binocular dissecting microscope. If amoebae were in- 

 cluded in the collection, they will be found particularly around the 

 rice grains. Pipette them off and begin separate cultures (p. 881). 



In order to collect parasitic Protozoa, one must, of course, find the 

 host organisms that harbor them. Various species of tadpoles, frogs, 

 cockroaches, termites, etc., which are of common occurrence or easily 

 obtained and which are hosts to numerous species of Protozoa, are 

 useful material for class work. 



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