PRIMARY FUNCTIONS OF THE ORGANISM 31 



myriad composing an organism. Both, however, 

 exhibit these primitive functions inherent in living 

 matter. At certain times Amoeba secretes about 

 itself a tough protecting membrane or cyst which is 

 the product of protoplasmic activity. Within this 



FIG. 9. Amceba proteus (much enlarged) : 1, nucleus; 2, contractile 

 vacuole ; 3, pseudopodia ; 4. food vacuoles ; 5, grains of sand. (From 

 Shipley and McBride, after Gruber.) 



cyst the living substance tides over unfavorable 

 periods, reproducing later in a characteristic way to 

 be described in another connection. Under favor- 

 able circumstances Amceba has been observed to 

 divide in two half -cells by a simple constriction and 

 severance of the cell. This process is preceded by 

 a division of the nucleus, so that each " daughter 



