Key to the Species 



1. Periplast decorated with spiral rows of pearly granules E. Spirogyra 



1. Periplast without spiral rows of granules — 2 



2. Cells a deep blood-red; haematochrome almost entirely 



masking the green pigment E. sanguinea 



2. Cells normally green ( if red, only temporarily 



so and then brick- rather than blood-red) 3 



3. Cells with a single, elongate, band-like or plate-like chloroplast 4 



3. Cells with other forms of or more than one chloroplast — — - 5 



4. Cells 55-60m long; organism maintaining 



its shape when swimming E. elongata 



4. Cells 12-14yu long; organism highly metabolic, constantly 



changing shape when swimming E. minuta 



5. Cells with convolute margins; paramylon bodies saucer-shaped, 



parietal along both sides of the cell , E. convoluta 



5. Cells with other shapes of paramylon bodies; 



margins not convolute 6 



6. Cells elongate-fusiform, produced posteriorly into a long, fine, 

 tapering point; 140-1 8O/-1 long E. acus 



6. Cells fusiform or somewhat cylindric, not produced into 



a long, fine point posteriorly — T 



7. Cells highly metaboHc, constantly changing shape in movements 8 



7. Cells not highly metabolic, more or less rigid and 



maintaining a constant shape in movements 13 



8. Cells minute, 5-6^ in diameter — - - - E. minuta 



8. Cells larger 9 



9. Cells stout, less than 5 times as long as wide — 10 



9. Cells longer than 5 times their diameter; 



elongate-fusiform or subcylindric .__ - 12 



10. Cells nearly cylindrical, or broadly fusiform, with 12-15 



chloroplasts; cells 80-90/x long - E. polymorpha 



10. Cells smaller, not cylindrical; 37-50-(95)m long 11 



11. Chloroplasts numerous, as many as 50; cells broadest 



below the midregion; 50-70- ( 95 )/x long E. proximo 



11. Chloroplasts not so numerous; broadest at or 



above the midregion; 37-50^ long E. gracilis 



12. Cells cyHndrical, broadly rounded posteriorly - 14 



12. Cells abruptly tapering posteriorly, forming a blunt tip - — E. deses 



13. Paramylon bodies in the form of rods; posteriorly narrowed to 



form a sharply pointed tip; cells small (66)-70-80m long E. tripteris 



13. Paramylon bodies in the form of 2 large, oblong 



rings; cells large, up to 500^ long - — - E. oxytiris 



14. Cells 76-lOOu long E. elastica 



14. Cells 250-290,u long E. Ehrenbergii 



Euglena acus Ehrenberg 1838, p. 112 



PI. 85, Fig. 28 



Cells very slightly metabolic, elongate spindle-shaped, produced 



posteriorly into a long, fine tapering point, narrowed and truncate 



at the anterior end; membrane indistinctly spirally striated; chloro- 



[ 390 ] 



