EUGLENA » 



1. Mount a drop of water containing Euglena, and examine with the 

 low power. The active specimens will be seen as green, elongated, free- 

 swimming organisms. When an individual is not actively swimming, it 

 generally shows certain characteristic squirming movements (euglenoid 

 movements) which result in marked changes in the shape of the cell, so 

 that the body may be almost spherical at times. 



2. Select a favorable specimen which is exhibiting euglenoid movements 

 and study it carefully under high power. Note the thin cell wall, or pel- 

 licle, which remains unbroken but readily responds to the flowing move- 

 ments in the cytoplasm. Make a series of ten outline drawings to show the 

 successive changes in the shape of a single individual. 



3. Study various specimens of Euglena with the high power. Distin- 

 guish the rather blunt anterior and the finely pointed posterior ends. 

 Note : (a) the flagellum which is attached in a depression at the ante- 

 rior end (careful focussing will be necessary) ; (b) the red pigment spot 

 (stigma) ; (c) the contractile vacuoles and reservoir which are seen 

 as a fight-colored area near the stigma ; (d) the nucleus. 



4. The green color of Euglena is due to chlorophyll which is present 

 in numerous disc-shaped chloroplastids quite uniformly distributed 

 through the cytoplasm. Other larger bodies (pyrenoids) can be noted 

 in some species, which are regarded as starch-forming centers. 



5. Make a drawing about 3 inches long showing all the observed struc- 

 tures. 



6. Occasionally, dormant individuals may be found which are almost 

 spherical in shape and surrounded by a rather thick cyst wall. Study 

 any such encysted specimens present in your preparation and make draw- 

 ings to show the structure as observed. 



7. Mount and examine a few drops of water from a laboratory cul- 

 ture containing various other common species of Flagellates, such as Mo- 

 nads, Peranema, Phacus, etc. Identify the various species present and 

 compare their general structure and activities with those of Euglena. 



(W. f. 23.) 



» B. pp. 29-33. 



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