UNIT AND DIVISION OF LABOR 141 



* 



Conclusions. 1. Does there seem to be an anterior or head 

 end as distinguished from a posterior or tail end ? Explain. 



2. Are these animals sensitive to their surroundings ; that is, 

 do they react, or respond, to stimuli ? Reasons for your deci- 

 sion ? 



2. FEEDING (OPTIONAL) 



Note. The food balls are small masses of food distributed throughout 

 the body. 



Method. Run a mixture of carmine and water under the cover glass. 



Observations. 1. Look for a diagonal groove where the food is taken 

 in (gullet). 



2. Can you make out any movements of cilia here as indicated by the 

 carmine grains ? 



3. In course of time, do you find any food balls within the body, as in- 

 dicated by the carmine ? 



Note. The masses of food appear to be inclosed in small areas, con- 

 taining fluid, called vacuoles. 



3. CONTRACTILE VACUOLES (EXCRETION) (OPTIONAL) 



Note. Other vacuoles, round clear openings, besides those containing 

 food, can commonly be seen, which are supposed to act to pass off waste 

 material from the cell body. These are called contractile vacuoles. 



Observations. 1. See if you can make out any changes in the shape 

 of these vacuoles. 



2. Do they close at times? 



4. REPRODUCTION (OPTIONAL) 



Observations. 1. Look for animals pinching into two parts, dumbbell 

 fashion. (If the material does not show it, refer to page 192, Hunter, 

 Essentials of Biology.') This is known as reproduction by division. 



2. Likewise can you find any fused together lengthwise side by side ? 

 This is known as conjugation. 



Conclusion. Sum up the method of reproduction in a paramcecium. 



b. As a Cell (Optional) 



Method. Use prepared slides or Figure 41. Can you find a cell 

 wall ? How can you tell nucleus from cytoplasm ? 



