CHAPTER XV 



REPRESENTATIVE PROTOZOA— EUGLENA, 

 AMOEBx\ AND PARAMECIUM 



EUGLENA, OF CLASS MASTIGOPHORA 



Habitat and Characteristics 



The most common species are Euglena viridis and Euglena gracilis 

 which are found abundantly in fresh water. This genus is also quite 

 well represented among marine animals ; many of the Euglenae possess 

 chloroplastids which give them the possibility of photosynthesis. They 

 are usually found living in the surface waters of ponds, sluggish 

 creeks, and lakes. Euglenae are sometimes classified as plants by 

 botanists because of the presence of chlorophyll. Euglena is a form 

 which illustrates certain plant characteristics and animal character- 

 istics in the same organism. 



Structure 



The microscopic, single-celled body has about the shape and pro- 

 portions of a cigar with a blunt anterior and a sharp posterior end: 

 At the anterior end, attached near the mouth, it bears a very slender, 

 almost transparent, whiplike filament, the flagellum. This is an ex- 

 tension of the cytoplasm. The superficial layer of the cell or ectosarc 

 (ectoplasm) is covered by an extremely thin portion, the cuticle. 

 Most of the eugienoid forms have spiral markings (striations) on 

 the surface of the body. The mouth of the cell is near the anterior 

 end, and extending inward from it is the gullet or cytopharynx. 

 Beside the cytopharynx is the reservoir or large vesicle. Just anterior 

 to this is the stigma, which is red in many individuals of E. viridis. 

 Bodies of collected protein material may be seen in connection with 

 most of the chloroplasts which are distributed through the cytoplasm. 

 These bodies are called pyrenoid bodies. Within the inner portion of 

 the cell or endosarc (endoplasm) is located the nucleus. It is usually 

 obliterated from view by the abundant chloroplasts. Small contractile 

 vacuoles empty from the endoplasm into the reservoir. 



282 



