64 



ORGANISMS OF ONE CELL - 



the organisms become gradually overpowered by the products 

 of their own metabolism, or that the formative processes are 

 not properly functioning. They also show that salts or elec- 

 trolytes were probably no longer present in the cells and that 

 oxidative processes had ceased, because the simple addition of 

 salts to the medium resulted in the restoration of vital activities. 

 Finally they indicate that the nucleus of the cell is probably the 

 seat of manufacture of the oxidative ferments or catalyzers. 



FIG. 27. Paramecium caudatum in the condition of depression and recovery 

 through the use of salts. The individual on the left has densely packed proto- 

 plasm, the others were similar individuals which were treated with potassium 

 phosphate. From photographs of prepared specimens. 



Reproduction. Like * Amoeba proteus and the flagellates, 

 Paramecium reproduces by simple division, the micronucleus 

 dividing first. The cell divides transversely through the 

 middle of the macronucleus which is passively divided with the 

 rest of the cell (Fig. 28). One new mouth and new contractile 

 vacuoles are formed by the daughter cells which separate and 

 begin an independent existence. The entire process requires 

 from half an hour to two hours according to the temperature. 



Irritability. Like Amoeba proteus again, Paramecium responds 

 to external stimuli, but having definite motile organs its re- 

 sponses are more definite and more easily studied. It answers 



