AMOEBA ■ 



1. Mount a few drops of water containing numerous large Amoebae. 

 Examine the preparation under a medium power (high-power eyepiece 

 with low-power objective). The animals will be seen as very small, 

 irregular, semi-transparent bodies composed of a jelly-like living material 

 (protoplasm) and generally containing numerous particles of various 

 shapes and colors which give it a granular appearance. When a large 

 Amoeba has been found, move the slide so as to bring the specimen exactly 

 in the center of the field, and then examine under the high power. Be 

 very careful not to lose the specimen when shifting to the high-power 

 objective. 



2. Study the specimen and note the absence of any visible cell wall and 

 the almost continual variations in the shape of the body due to the forma- 

 tion of irregular processes (pseudopodia) from any part of the surface. 

 Note that the animal moves slowly from place to place. Try to explain 

 how this is accomplished. Make a series of outline drawings — at least 

 ten — at one-minute intervals to show the changes in the shape of the 

 Amoeba under observation. Indicate in each drawing, by means of ar- 

 rows, the direction the animal is moving. 



3. Study an Amoeba carefully under the high power and note that there 

 is a differentiation of the protoplasm into (a) an outer transparent layer 

 of ectoplasm and (6) an inner granular region of endoplasm. This 

 arrangement can be seen clearly in the pseudopodia. The endoplasm 

 contains (c) the nucleus which usually is seen as a spherical, granular 

 body ; (d) numerous gastric vacuoles in which are various kinds of food 

 materials in the process of digestion ; (e) a spherical contractile vacuole 

 which gradually increases in size as the liquid wastes accumulate until a 

 certain size is reached. Then it suddenly contracts, and discharges the 

 wastes to the exterior. Make a drawing, about 3 inches in length, of an 

 Amoeba to show the detailed structure of this animal. 



4. Make careful observations of an Amoeba which is moving actively 

 and note the reaction of the ectoplasm to the various bits of debris with 

 which it comes in contact. If care is taken, it is often possible to observe 

 the manner in which an Amoeba rejects inorganic material with which it 

 comes into contact, ingests food particles, and egests the indigestible refuse. 



1 B. pp. 19-28. 

 257 



