358 Animal Biology 



is) (L. gracilis, slender). These flagellates belong to the class Masti- 

 gophora (mas ti -gof o ra) (Gr. mastix, whip; phoreo, to bear) because 

 of a whiplike flagellum (L. flagellatus, whip). Because Eugle Ji a has 

 certain plantlike characteristics, it is frequently claimed to be a plant by 

 the botanists. We might well compromise and call it a plant-animal, 

 E. viridis is about 0.1 mm. long, blunt at the anterior end, and with a 

 pointed posterior end. An ovoid or spherical nucleus contains a central 

 body, the endosome (Fig. 173). 



Mouth 



Gullet-M' 



Stigma 



Granules 



Pyrenoid' 

 Nucleus— 



Striation 



Reservoir 



-Contractile 

 vacuoles 



Nucleus, 



Cuticle 



Chromatophore ^ 



B 



y Flagellum -^ 



[($^t^)— Chromatophore- 



-Reservoir — 



—Nucleus 

 Cyst 



Fig. 173. — Euglena viridis, a protozoan of the class Mastigophora. A, Free- 

 swimming adult (highly magnified) ; B, reproduction by longitudinal binary fis- 

 sion; C, euglena rounded and protected by cyst; D, longitudinal fission within 

 cyst; E and F, shapes (in outline) assumed by Euglena. (All enlarged and some- 

 what diagrammatic.) 



Integument (Covering). — A tough, flexible, external pellicle (cuticle) 

 has longitudinal, parallel, thickened striations which give the body 

 rigidity. 



Ingestion and Digestion. — A funnel-shaped cytostome (cell mouth) 

 leads to a cytopharynx (gullet). The latter has an enlarged reservoir 



