CHAPTER XXI 

 AMOEBA AND SOME ALLIES: PROTOZOA 



Gradual, from these what numerous kinds descend, 

 Evading even the microscopic eye ! 

 Full nature swarms with life, one wondrous mass 

 Of animals, or atoms organized. 



JAMES THOMSON, Summer. 



Amoeba. The amoeba (Amce'ba pro' tens, Fig. 140) is com- 

 mon in stagnant water of all lands, but it is so minute 

 that it is impossible to be sure of its presence in a given 

 place until examination has been made with a compound 

 microscope. 



One of the best ways to find large specimens of the 

 amoeba is to remove carefully from the bottom of a well- 

 stocked fresh-water aquarium a few dead leaves. A medi- 

 cine-dropper full of material from the surface of one of the 

 leaves may yield several specimens. A short time after a few 

 drops of the water have been mounted on a glass slide the 

 Amoebae will exhibit the characteristic structure and activities. 

 The usual diameter of an amoeba is about .5 mm. (^ inch). 



The beginner in microscopy is very likely to overlook an 

 amoeba altogether, or to think in his anxiety that every little 

 irregular clear spot in the field of his microscope-objective 

 is one. The active amoeba is never the same in appearance in 

 consecutive moments. The outline, at all times irregular in 

 locomotion, constantly becomes more or less so, by the increase 

 or decrease in prominence of little processes called pseudo- 

 podia (false feet), which extend in one or several directions. 



Amoeba is a complete organism, although it is composed of 

 a single cell. The substance of the cell is protoplasm, that 



