CHAPTER XV. 



PROTOZOA. 







AMCEBA. 



AMCEB^E are to be found in standing water, where they live in 

 the slimy coating on the leaves and stems of submerged plants, 

 or on the upper layer of mud or ooze at the bottom. Such water 

 with mud and plants should be collected sometime beforehand 

 and kept undisturbed in the laboratory. 



1. Take a drop of water from the bottom or the surface of a 

 leaf, mount on a slide, and cover with a cover slip. Examine 

 with a high power of the microscope, using a one-fifth or a 

 one-sixth inch objective. 



2. General Appearance. An amoeba looks like a small drop 

 of clear jelly, but after watching it a short time it may be seen 

 to change its form. The body is composed of a substance called 

 protoplasm. 



3. Structure. The following parts should be identified : 



a. A clear outer margin, the ectosarc. 



b. A dotted or granular inner portion, the endosarc. 



c. A denser, spherical body within the endosarc is the nucleus. 



d. A clear space that from time to time contracts and dis- 

 appears. This is the contractile vesicle or vacuole. Are its 

 pulsations regular ? Time them. 



e. Other vacuoles that do not pulsate but are filled with 

 granules of food materials. These are called food vacuoles. 



4. Movements. Watching the amoeba closely shows that it 

 not only changes its form, but also its position ; it not only 

 moves, but moves from place to place. It has not only motion, 

 but locomotion. By closely watching an amceba it may be seen 



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