26 PROTOZOA 



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 jood 

 vacuoles. What do you think is probably the nature of 

 the fluid in the vacuoles? In watching them do you notice 

 any definite movement of the protoplasm? Try to see the 

 undigested 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 compressed specimens the contractile vacuoles and their 

 reservoirs are usually conspicuous. Note the order of ap- 

 pearance 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, de- 

 void of granules but containing radially arranged, minute, 

 oval bodies, the trichocysts, is just internal to the cuticle. 

 The inner mass of protoplasm, containing the contractile and 

 food vacuoles, and small granules, is the endoplasm. 



6. If possible distinguish the clear, centrally located 

 nucleus (macronucleus) . 



Make a sketch showing all of the above points. 



7. Kill the animal by running a drop of methyl green 

 under the coverglass. What happens to the cilia? It is pos- 

 sible to watch the process of staining in the macronucleus 

 if specimens are observed very soon after the methyl green 

 is added. In Paramecium caudatum the micronucleus may 

 also be seen. If P. aurelia is being studied the micronuclei 

 usually cannot be detected by this method. 



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

 placing them in a solution of quince-seed jelly or by teasing a small 

 piece of lens-cleaning paper in the medium containing the paramecia. 

 Specimens so treated remain alive for some time. 



