THE PARAMECIUM 73 



which function as do the contractile vacuoles of other forms. Examine 

 stained demonstration specimens showing the nucleus, and add it to 

 your drawing. 



(e) If the flagellum has not been observed, prepare another slide 

 and stain with iodine or methyl violet. Find the flagellum attached 

 to the anterior end of the cell and add this to the figure. 



(f) Reproduction by longitudinal fission may be observed in the 

 living material, or stained demonstrations may be studied. Draw 

 dividing specimens if they are available. 



Exercise 3. — Encysted Phase. 



(g) Encysted euglense are often found in cultures that have been 

 standing for some days in the laboratory; or they may be collected 

 in nature. Examine such material, and find the euglense surrounded 

 by cysts. Note any structures identified in the active animal. Do 

 you find individuals that have reproduced by cell division while en- 

 cysted? Understand from lectures or textbook the relation between 

 the active and encysted phases of the life-cycle. Draw several indi- 

 viduals in the encysted condition, including reproducing individuals 

 if seen. 



THE PARAMECIUM 



Phylum Protozoa Class Ciliata 



Exercise 1. — Occurrence and General Activities. 



(a) The Paramecium is one of the unicellular forms most easily 

 obtained. The species Paramecium caudatum is commonly studied. 

 In nature, the animals are most abundant where the water is foul and 

 ill-smelling, as in streams containing sewage and other decomposing 

 organic material. Examine the laboratory cultures and note how they 

 differ from cultures of amoebse and euglense. Can the animals be seen 

 without any magnification? Do they tend to collect at certain places 

 in the culture jars? 



(b) Fresh material will be distributed on slides. Do not add a 

 cover glass at first; but examine with the low-power objective, noting 

 the rapid movements and general behavior. Watch a single individual 

 as it moves about. What determines the direction of its locomotion? 

 Does the animal act as though it profited by experience? Determine 

 its exact shape. How does the anterior end differ from the posterior 

 end? Does the animal exhibit symmetry of any kind? 



