AMCEBA AND SOME ALLIES 291 



are highly important as parasites of man and other higher 

 animals. In man one type of dysentery is produced by an 

 amoeba, and many diseased conditions are due to amoeboid 

 forms. 



Euglena. A relative of Amoeba, found in the same situ- 

 ations, is Eugle'na vir'idis (Fig. 151) ; it also is composed of 

 one cell. Euglena has a more fixed arrangement of parts 

 than Amoeba. There is a blunt anterior end with a short, 

 funnel-shaped mouth. Out of the mouth extends a long 

 lash, or flagellum, which by its whip-like vibrations carries 



Fig. 151. Euglena. (Much enlarged) 

 After Saville Kent 



the animal through the water. Behind the mouth is a small 

 red eye-spot, which lies beside a clear space. This clear space 

 has been found to be sensitive to light. The nucleus is near 

 the middle of the body, and can be seen easily in the liv- 

 ing animal, although the cytoplasm immediately about it is 

 colored quite green with chlorophyll, — a coloring matter 

 found in the green parts of plants. 



Many biologists believe that Euglena is indeed a plant 

 because, through the agency of its chlorophyll, it can use 

 carbon dioxide as a raw food material, retaining the carbon 

 and giving off oxygen when the organism is in the light. 

 This creature illustrates the fact that it is impossible to 

 classify all organisms as plants or animals. 



As a rule Euglena moves with the lash forward, but the ani- 

 mal can turn in any direction, and can even change the shape 



