III. 



THE PROTEUS ANIMALCULE (Amoeba). 

 COLOURLESS BLOOD CORPUSCLES. 



Amcebcz are minute organisms of very variable size which 

 occur in stagnant water, in mud, and even in damp earth, 

 and are frequently to be obtained by infusing any animal 

 matter in water and allowing it to evaporate while exposed 

 to direct sunlight. 



An Amoeba has the appearance of a particle of jeliy, 

 which is often more or less granular and fluid in its central 

 parts, but usually becomes clear and transparent, and of a 

 firmer consistency, towards its periphery. Sometimes Amoeba 

 are found having a spherical form and encased in a struc- 

 tureless sac, and in this encysted state they exhibit no 

 movements. More commonly, they present incessant and 

 frequently rapid changes of form, whence the name of 

 "Proteus Animalcule" given to them by the older ob- 

 servers; and these changes of form are usually accompanied 

 by a shifting of position, the Amoeba creeping about with 

 considerable activity, though with no constancy of direction. 



The changes of form, and the movements, are effected by 

 the thrusting out of lobe-like prolongations of the peripheral 

 part of the body, which are termed pseudopodia, sometimes 

 from one region and sometimes from another. Occasionally, 

 a particular region of the body is constantly free from 

 pseudopodia, and therefore forms its hindmost part when 



M. 2 



