A FLAGELLATE 157 



These are minute globules of clear liquid, which represent the ex- 

 cretory wastes of the animal; they collect and discharge into 

 the reservoir periodically, which thus acts as a urinary bladder 

 and in turn opens into the gullet. Near the reservoir is a red 

 pigment spot, which is sensitive to light ; it is the most primitive 

 form of an eye. 



Exercise 2, Draw Euglena on a large scale with the organs mentioned. 



In its life processes Euglena partakes of the nature of both 

 a plant and an animal. Through the agency of the chlorophyll, 

 bodies of greater or less size called pyrenoids are manufactured ; 

 these produce carbohydrates, which constitute a large part of 

 the food of the organism. The process goes on only during the 

 daytime and is a characteristic plant process. But Euglena also 

 ingests solid food after the manner of animals. Bacteria and 

 other food particles are taken into the mouth at the anterior end 

 and thence sink into the soft, protoplasmic body. Excretion is 

 effected through the pulsating vacuoles ; respiration, through the 

 body surface. 



From time to time Euglena encysts itself. It loses its flagel- 

 lum, draws itself together into a spherical form, and secretes a 

 cyst of cellulose. After a while it either throws off the cyst and 

 assumes its former shape or reproduces by dividing into from two 

 to eight small Euglenas. Reproduction thus takes place during 

 the period of encystment ; also at times free individuals reproduce 

 by longitudinal division. 



Exercise 3, Among a large number of individuals look for dividing 

 and also for encysted ones. Make large drawings of several. 



