REFERENCE BOOKS 135 



Problem 113 : Comparative study of various forms of single- 

 celled animals to explain division of labor. (Extra Problem.) 



Materials. Figures on opposite page showing amoeba, paramce- 

 cium, vorticella, and a colonial form, such as charchesium or zoo- 

 thamnium. 



Observations. Examine the figure of an amceba. Are there 

 any special structures for locomotion? The entire cell body 

 changes shape as the animal moves. Has the animal any definite 

 mouth? Gullet? Look at the figures. How is food taken into 

 the body? Look for food vacuoles, contractile vacuoles, nucleus. 



Compare an amceba with a paramoecium. In which cell is 

 the work performed by more separate parts of the cell? 



NOTE. The performance of different kinds of work by different structures in 

 a plant or animal is called division of labor. 



Compare the amceba and paramoecium with vorticella. Note 

 the stalk ; it is contractile. Is the entire body covered with 

 cilia ? Are the cilia used for the same purpose as in paramoecium ? 

 Is there a definite food opening? How does food get into this 

 opening ? (Demonstration of a vorticella in a weak carmine mix- 

 ture will show this point.) 



Look at the colonial form. How does it differ from vorticella? 

 How does it move? How is food obtained? Is there greater or 

 less division of labor than in a single cell ? 



Conclusion. What is division of labor? Explain from com- 

 parison with at least three one-celled animals. 



'PROBLEM QUESTIONS 



1. Explain the term " reaction to stimuli " with reference to 

 paramcecium. 



2. What parts of a cell are found in paramcecium? 



3. How does paramcecium move? Feed? Breathe? Re- 

 produce ? 



4. How is division of labor illustrated among the Protozoa ? 



REFERENCE BOOKS 



Hunter, Civic Biology, Chap. XIII. American Book Company. 

 Hunter, Elements of Biology, Chap. XII. American Book Company. 



