CHAPTER 4 



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Phylum Protozoa. 

 Flagellates 



EiE flagellates are protozoa that differ 

 from the amoeba in that they usually pos- 

 sess a definite shape and a front end from 

 which arise one or more whiplike locomotor 

 organelles called flagella (singular flagel- 

 lum). The flagella are also used to capture 

 food and to serve as sense receptors for ex- 

 ploring the surroundings. The flagellates are 

 abundant in puddles, ponds, and swamps. 

 Unfortunately, most of them are so small 

 that they are difficult to study. The euglenas, 

 however, are comparatively large and exhibit 

 most of the characteristics peculiar to the 

 class. 



One of the flagellates, the Phytomona- 

 dida, includes a number of colonial species 

 that can be arranged in a series, from a sim- 

 ple aggregation of cells as in Spondylomorum 

 (Fig. 401, p. 562), to a very complex colony 

 such as Volvox (Fig. 22). These flagellates 

 and certain others are of particular interest 

 since they combine the characteristics of 

 both plants and animals and are frequently 

 claimed by botanists. Many different species 

 live in fresh and salt water. With diatoms, 

 they constitute an important part of the 

 food supply for very small aquatic animals. 

 Many flagellates are parasitic in man, lower 

 animals, and plants. Some parasitic forms 

 are mentioned here, but a fuller discussion 

 will be found in a subsequent chapter. 



EUGLENA VIRIDIS 



Habitat 



One of the common species of the genus 

 Euglena, usually Euglena viridis, ordinarily 

 serves as a type of the class Mastigophora. 

 Euglenas are common in fresh-water ponds, 

 to which they give a greenish tinge if present 

 in sufficient numbers. They are usually found 

 in collections of pond weeds and thrive in 

 the laboratory in a jar on the window sill 

 where there is plenty of indirect sunlight. 

 Over 150 species have been described in the 



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