CHAPTER XX. 

 THE AMCEBA. 



THE Amoeba, or Proteus animalcule, consists of a minute irre- 

 gular particle of jelly-like protoplasm (Fig. 103, A.). Individuals 

 may generally be found in animal and vegetable infusions or in 

 stagnant pond water. Each looks like a little patch of some- 

 what cloudy white of egg ; but, if it be carefully watched, it will 

 be found to be constantly changing its form, and moving slowly 

 across the stage of the microscope by pushing out blunt processes 

 or pseudopodia (ps.). Careful observation discloses an external 

 cortical layer, the ectosarc or ectoplasm, enclosing the inner sub- 

 stance, endosarc or endoplasm. The ectoplasm is clear, the endo- 

 plasm granular. When a pseudopodium is pushed out the ecto- 

 plasm precedes the endoplasm, which follows with a kind of 

 rush. Within the granular endoplasm there is at least one,, 

 sometimes more than one, rounded endoplast (TI.), with a smaller 

 endoplastule within it. A rhythmically pulsating contractile 

 vesicle (c. v.) exhibits the usual slow diastole and sudden 

 systole. Oily granules, crystals, and food-vacuoles may also 

 be seen to flow hither and thither within the endoplasm in 

 vague circulation. 



Food is taken in at any point of the body, and the indiges- 

 tible residue is also extruded at any point. There is not even a 

 potential mouth or anus. Sometimes a pseudopodial process 

 seems to be wrapped over the morsel of food, in which case 

 some of the ectoplasm becomes internal. It must be remem- 

 bered, however, that the differentiation into these two layers is 

 of the slightest. 



The amoeba multiplies by fission. After attaining a certain 



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