Unicellular, Microscopic Animals 359 



at its base. A contractile vacuole next to the permanent reservoir arises 

 by the flowing together of several smaller vacuoles, and it discharges 

 wastes into the reservoir. 



Suspended in the cytoplasm are numerous green, chlorophyll-bearing 

 chromatophores (kro' mat o for) (Gr. chroma, color; phorein, to bear) 

 known specifically as chloroplasts. In each chloroplast is a pyrenoid (pi- 

 re' noid) (Gr. pyren, fruit-stone; eidos, like) which probably forms a 

 starchlike paramylum (pa -ram' i lum) (Gr. para, beside; amylon, 

 starch). The latter may be free in the cytoplasm in the form of rods, 

 disks, etc. Euglenae photosynthesize most of their foods (holophytic 

 nutrition) in a plantlike manner, although they may absorb certain foods 

 through the general body surface by saprophytic nutrition. It is debated 

 whether Euglenae ingest solid foods through the cytopharynx. 



Motion and Locomotion. — A long, vibratile flagellum, arising from two 

 axial filaments within the body, extends out through the cytostome. The 

 flagellum consists of a contractile axial filament, or myonemes (mi' on- 

 em) (Gr. myo, muscle; nema, thread), composed of a bundle of fibers 

 and surrounded by a sheath of protoplasm. A Euglena may be propelled 

 in a spiral path by the actions of the flagellum at the anterior end. Eu- 

 glena may also contract the body to assume a variety of shapes and to 

 move by what is called euglenoid movement. 



Circulation. — Foods, wastes, etc., are circulated through the cytoplasm 

 by the flowing of the protoplasm and is known as cyclosis. 



Respiration. — Respiration takes place through the general body sur- 

 face. Possibly some of the carbon dioxide is used in photosynthesis, and 

 some of the oxygen from photosynthesis is used for its various activities. 



Excretion. — A contractile vacuole, next to the permanent reservoir, 

 arises by the flowing together of several smaller vacuoles and collects and 

 discharges wastes into the reservoir. From the latter the wastes pass to 

 the gullet and out the cytostome. It is not unusual for wastes to be elim- 

 inated through a mouthlike opening in lower types of animals. 



Coordination and Sensory Equipment. — A light-sensitive, red, eye spot 

 or stigma (Gr. stigma, mark) is near the anterior end of the body. A 

 fine, delicate, fiberlike rhizoplast (ri'zoplast) (Gr. rhiza, root; plastos, 

 formed) extends from the nucleus to the reservoir. Euglenae swim to- 

 ward ordinary light (positive phototaxis) to assist in photosynthesis but 

 swim away from direct sunlight which may be harmful. The avoiding 

 reaction is frequently observed. 



