46 A GUIDE FOR THE STUDY OF ANIMALS 



Protozoa (first animals), animals of one cell, existing alone 

 or in loose colonies. 



Observations. 



1. Examine a single cell, stained to show structure. 

 Identify the nucleus, cytoplasm, and, if present, the 

 nucleolus or the micronucleus, and the cell wall. Draw to 

 show the form of the cell and the details of its structure. 

 Label all details. 



2. Examine some stained paramecia. Select a typical 

 one and identify in it nucleus, micronucleus, cytoplasm, 

 and cell wall or cell membrane. You may also be able to 

 see vacuoles, looking like holes in the stained protoplasm. 

 Give reasons for considering this animal to be a single cell. 

 Draw one, to show its cellular structure. Label all details. 



3. Clean a slide and cover glass, place a drop of water 

 containing living paramecia on the slide, cover it, and 

 examine. What structures do you see which you saw in 

 the stained paramecia .■' What structures do not show } 

 Identify any new structures you may observe. Identify also 

 the leading end and the side containing the oral groove. 



4. Describe the shape of the animal. 



What is the actual length of the animal ? 



5. After watching the animal for some time, describe 

 the path followed by a given specimen as it crosses the 

 field of the microscope. What reason can you see, if any, 

 why this paramecium is moving "i What external factors, 

 if any, seem to determine the path it follows .■' 



6. How rapidly do paramecia really move .' What 

 structures do they use in locomotion } 



How do they manage to move in one direction, instead of alternately 

 backward and forward ? How do they manage to move in a straight 

 line, though their bodies are not symmetrical ? 



