EUGLENOIDINA 235 



central, numerous chromatophores hemi-lenticular; several small 

 rod-shaped paramylon bodies scattered; flagellum short. 



E. gracilis Klebs (Figs. 39, a-d; 101, h). 35-55m by 6-23m; cylin- 

 drical to elongated oval; highly plastic; flagellum less than body 

 length; fusiform chromatophores 10-20, discoid; nucleus central; 

 pyrenoids. 



E. rubra Hardy. 70-170^ by 25-36//; cylindrical, rounded anteri- 

 orly and drawn out posteriorly; pellicle spirally striated; nucleus 

 posterior; flagellum longer than body; the base of flagellum ar- 

 ranged as in E. acus (Fig. 24) ; stigma about 7)U in diameter, lateral 

 to the reservoir, near which a contractile vacuole is formed; chro- 

 matophores, many, spindle-shaped, with 3 longitudinal grooves; 

 when taken out of body disc-shaped; haematochrome granules red, 

 numerous, measure 0.3-0.5iu in diameter; paramylon bodies, numer- 

 ous, ellipsoid; reproductive and temporary cysts and protective cysts 

 (34-47/i in diameter), with gelatinous coat; multiplication noted 

 only in encysted forms (Johnson). 



Johnson (1939) found that the color of this Euglena was red in 

 the morning and dull green in the late afternoon, due to the dif- 

 ference in the distribution of haematochrome within the body. 

 When haematochrome granules are distributed throughout the 

 body, the organism is bright-red, but when they are condensed 

 in the center of the body, the organism is dull green. When part 

 of the area of the pond was shaded with a board early in the 

 morning, shortly after sunrise all the scum became red except 

 the shaded area. When the board was removed, the red color 

 appeared in 1 1 minutes while the temperature of the water remained 

 21°C. In the evening the change was reversed. Johnson and Jahn 

 (1942) later found that green-red color change could be induced by 

 raising the temperature of the water to 30-40°C. and by irradiation 

 with infrared rays or visible light. The two workers hold that the 

 function of haematochrome may be protective, since it migrates to a 

 position which shields the chromatophores from very bright light. 

 If this is true, it is easy to find the species thriving in hot weather in 

 shallow ponds where temperature of the water rises to 35-45°C. In 

 colder weather, it is supposed that this Euglena is less abundant and 

 it exists in a green phase, containing a few haematochrome granules. 



E. vermiformis Carter. 45ju by 5/x; without flagellum; a slow spiral 

 movement; retains cylindrical form during locomotion; among de- 

 bris; stigma conspicuous; delicate pellicle not striated; about 8 pe- 

 ripheral chromatophores; many small paramylon bodies in the form 

 of flattened elliptical rings; brackish water. 



