THE AMOEBA 



11 



Amoeba ends in death after a period of time al^oiit the same 

 as that of a normal A^noeha which has been starved. 

 This indicates that the function of the nucleus is to control 

 metabolism and reproduction rather than to maintain the 

 activities of the Amoeba as a whole. 



Usually one large water- or contractile-vacuole can be seen, 

 which from time to time contracts and squirts a liquid out of 

 the body. This is probably an osmotic organ controlling the 



Fig. 2. Amoeba profeus. x 330. From Gruber. 1. Niiclcua. 

 2. Contractile vacuole. 3. Pseudopodia ; the dotted line points 

 to the clear ectoplasm. 4. Food vacuoles. 5. Grains of sand. 



amount of water which has passed by osmosis into the saline 

 protoplasm. Without such an organ the cell might biu'st. 

 The waste products are got rid of from the general surface 

 of the cell, for if they accumulate they interfere with the life 

 of the Amoeba, just as too many ashes put out a fire. 



A recent device enables us to dissect organisms as small as 

 Amoebae, under the microscope. Exceedingly fine glass needles 

 are used. The contents of the contractile vacuole if stirred 

 up with the surrounding jirotoplasm by means of such a 

 fine needle cause a very rapid and complete break-up, 



