EUGLENA, AMOEBA, AND PARAMECIUM 



283 



Food and Assimilation 



The food problem among Euglenae as a group is interesting from 

 the biological standpoint. It seems that some Euglenae are able 

 to ingest other small organisms through the mouth and cytopharynx 

 to be digested in a vacuole within the endoplasm; this has been 

 called holozoic nutrition as typical of animals. E. viridis probably 

 does not possess this possibility. Others, like E. gracilis, are able to 



CONTRACTILE VACS: 

 RESERVOIR 



CHROMATOPHORES _jJw»T-ai f- ^^.- „^ 



CUTICLE- ^^S-d^^i%l^ 



MUCLEU3 



Fig. 93. — Euglena viridis, a chlorophyll-bearing flagellate. (From Parker anil 

 Clarke, Introduction to Animal Biology, The C. V. Mosby Company.) 



assimilate dissolved nutriment by absorption through the general cell 

 surface (saprophytic nutrition). In fact, this species has been main- 

 tained for more than two years in a nutrient solution in darkness. 

 Those forms like E. viridis that are abundantly endowed with chloro- 

 phyll obtain their food largely by photosynthesis as does the green 

 plant. This process utilizes water, carbon dioxide, dissolved mineral 

 salts, and with the aid of light and chlorophyll builds up organic food 

 substances. The final stage of the carbohydrates formed by this 



