PARAMECIUM — AMOEBA 



99 



Mouth 



Micronudeus 



Macronucleus 



Reproduction of Paramecium. — Sometimes a Paramecium may 



be found in the act of dividing into two by the process known 



as fission. Each of the new cells contains half 



of the original cell. The original cell may thus 



form in succession many hundreds of cells in every 



respect like the original parent cell. A process 



which appears to stimulate reproduction is called 



conjugation. Of this more will be told later. 

 Amoeba.^ — In order to understand more fully 



the life of a simple bit of protoplasm, let us take 



up the study of the amoe'ha, a type of the simplest 



form of animal life. Unlike the plant and animal 



cells we have examined, the amoeba has no fixed Paramecium dividing 



form. Viewed under the compound microscope, ^ 



it has the appearance of an irregular mass of granular protoplasm. 



Its form is constantly changing as it moves about. This is due to 



the pushing out of tiny pro- 

 ^^ '^^-^ '^ ""^"^ ^x-^^""^^ ^i jections of the protoplasm 



of the cell, called pseudopo- 

 dia (su-d6-po'di-d ; false 



How an amcBba moves (side view). 



Contractile 

 vacuole...! 



Nucleus.. 

 Food 



feet). The locomotion is accomplished by a streaming or flowing 

 of the semifluid protoplasm. The pseudopodia push forward in 

 the direction in which the animal is 

 to go, and the rest of the body fol- 

 lows. In the central part of the cell 

 is the nucleus, a spherical structure, 

 seen more easily when the animals 

 are killed and stained. 



Although but a single cell, still the 

 amoeba responds to the stimulus of 

 food when it is near at hand. Food 

 may be taken into the body at any 

 point, the semifluid protoplasm sim- Pseudopodium. 



Living amoeba seen through a 

 1 Amoebae may be obtained from the hay in- microscope, 



fusion, from the dead leaves in the bottom of 



small pools, from the same source in fresh-water aquariums, from the roots of duck- 

 weed or other small water plants, or from green algae growing in quiet localities. 

 No sure method of obtaining them can be given, except to procure them from some 

 good supply house when needed. 



Ectoplasm 



fndoplasm 





