THE AMCEBA. 15 



Minute Structures. If the currents in an active amoeba 

 have been watched carefully under high power, certain 

 minute structures will have been discovered within the 

 body. Three of these are normally present, though not 

 always easily made out : 



1. A nucleus, a discoid or spherical body slightly more 

 transparent than the surrounding endosarc, and usually 

 located toward the posterior end of a moving amoeba. 



2. A contractile vesicle, a round clear spot within the 

 ectosarc. It may sometimes be seen to contract, and dis- 

 appear temporarily, and will then be certainly recog- 

 nized. 



3. Ingested food particles. These appear darker than 

 the surrounding endosarc ; or if colored food particles have 

 been taken, microscopic green plants, etc., the color will 

 shine through. These are of various sizes. 



These structures may be more readily made out in a 

 specimen that is stained with iodine. Place a drop of 

 iodine solution on the slide at one edge of the cover glass, 

 and place a bit of blotting paper at the opposite edge. 

 The blotting paper, by its absorbent action, will draw the 

 iodine solution under the cover glass, where it will pene- 

 trate and stain and kill the amoeba. The nucleus will be 

 more brightly stained than the other parts. 



Make an enlarged drawing of an amoeba prepared in this 

 way, showing all the points of structure you have been 

 able to see. 



By mixing some very finely powdered carmine or indigo 

 in the drop of water containing amoebas before covering, 

 their feeding may sometimes be better observed. 



Occasionally an amoeba may be found dividing into two. 

 Such should be watched carefully. 



The Life Process. The jelly-like living substance which 

 makes up the body of the amoeba is protoplasm. It is 



