EUGLENA 173 



Study the structure of the body. The protoplasm composing 

 it is clear, its surface often showing delicate striations. Note 

 the cuticula. In the middle of the body is a spherical nucleus. 

 At the anterior end near the depression is a clear space called 

 the reservoir ; find it. It receives the discharges of the pulsating 

 vacuole. This vacuole is a minute globule of clear liquid, which 

 represents the excretory wastes of the animal ; it collects and 

 discharges into the reservoir periodically, which thus acts as a 

 urinary bladder and in turn opens into the anterior depression. 

 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 above- 

 mentioned organs. 



In its life processes Euglena partakes of the nature of both a 

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

 starch-like carbohydrate called paramylum is manufactured, which 

 constitutes a large part of the food of the organism. The pro- 

 cess goes on only during the daytime and is a characteristic plant 

 process. But Euglena also ingests solid food after the manner 

 of animals. Food particles are taken into the depression at the 

 anterior end and thence sink into the soft protoplasmic body. 

 Excretion is effected through the pulsating vacuole ; respiration, 

 through the body-surface. 



From time to time Euglena encysts itself. It loses its 

 flagellum, 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 divid- 

 ing 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 divid- 

 ing and also for encysted ones. Make large drawings of 

 several. 



