12 PROTOZOA. 



INFUSORIA. . 



PARAMECIUM. 



Place a drop of the culture on a slide, cover, and examine 

 with the low power. 



1. In an animal not closely confined note the shape and 

 movements. Is it possible to distinguish an anterior and a 

 posterior end? A forward and backward movement? Is one 

 side of the animal kept constantly uppermost ? Is there a dorsal 

 and ventral surface? Do the animals change their shape either 

 permanently or temporarily? Individuals tend to collect about 

 air-bubbles and at the edge of the cover-glass. Why? 



Indicate by a sketch all the points which can be determined 

 with the low power. 



2. Draw off all superfluous water by means of filter-paper, 

 add a trace of powdered carmine, and then find a specimen 

 which is narrowly confined and examine it with the high power. 



The particles of carmine are taken into the body. Deter- 

 mine how and where. Note that the carmine collects in gastric 

 vacuoles. What do you think is probably the nature of the 

 |luid in the vacuoles? In watching them do you notice any 

 definite movement of the protoplasm? Try to see the undi- 

 gested material ejected. 



3. Determine the arrangement of the cilia, and the nature 

 of their motion. Is there a reversal of the direction of the stroke, 



etc.? 1 



4. Observe the contractile vacuoles. How many are there? 



Is their position constant? What is their action? In com- 

 pressed specimens the contractile vacuoles and their reservoirs 

 are usually conspicuous. Note the order of appearance and 

 disappearance of the vacuoles and reservoirs. 



5. Focus carefully on the margin of the body and note a very 

 thin outer cuticle. A thick layer, the ectoplasm, devoid of gran- 

 ules but containing radially arranged, minute, oval bodies, the 



trichocysts, is just internal to the cuticle. The inner mass of 



1 It is possible to decrease the rate of movement of the animals by placing 

 them in a solution of quince seed jelly. Specimens so treated remain alive 

 for some time. 



