EUGLENA 



(Materials: filter paper, aqueous iodine) 



Classification : — Phylum Protozoa, Class Mastigophora, Or- 

 der Eugienoidina. 



1. Secure a drop of Euglena culture from preparation 

 table. Euglena may be recognized as bright green spindle- 

 shaped or cigar-shaped organisms though some of the largest 

 species are rather distinctly flattened. 



2. Is there a characteristic shape? If your specimen is 

 undergoing changes in shape, make six sketches showing pro- 

 gressive change of form. 



3. Note that the body is composed of a thin outer layer of 

 ectoplasm covering an internal mass of endoplasm. 



4. Look for chromatophorcs or masses of chlorophyl which 

 give the body its green color. Shape of individual chromato- 

 phorcs? In which body layer? 



5. Locate stigma or red eye spot near the anterior end of 

 the body. 



6. The clear area, not occupied by chromatophorcs, in con- 

 tact with the eye spot is the reservoir of the contractile vacuoles. 

 The numerous individual vacuoles are not distinguishable under 

 ordinary magnifications. 



7. The reservoir opens into the gullet but in most species 

 the nature of the gullet is not recognizable under ordinary mag- 

 nification. The external opening of the gullet, the mouth, is 

 usually distinguishable as a small cleft in the anterior extremity 

 of the body. 



8. The flagellum passes through the mouth and under very 

 high magnification an attachment to the wall of the gullet has 

 been observed. Adjust light and focus carefully to see the long, 

 very fine flagellum. If not observable after a reasonable search, 

 add a drop of aqueous iodine to the water under the coverglass. 

 This kills the Euglena but in so doing colors the flagellum and 

 all other protoplasm brown. 



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