REFERENCE BOOKS 135 



Problem ll'i : Cm)V])aratJve stitfhjof rarious fnmvfiof siti^le- 

 ceUecl atUmals to cxplaiiv division of labor. (Kxtra Problem.) 



Materials. — Figures on opposite page showing amoeba, paranioe- 

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

 thamnium. 



Observations. — Examine the figure of an amoeba. 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 amoeba 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 dififercnt structures in 

 a plant or animal is called division of labor. 



Compare the amoeba 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 lal)or? Explain from com- 

 parison with at least three one-celled animals. 



Problem Qu?:stions 



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

 paramoecium. 



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



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

 produce ? 



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



Refehence Books 

 Hunter, Ciinc Biology, Chap. XIII. AmericMM iiook ('()mi»:tiiy. 

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



