Effect of Chemicals on Growth 



501 



The table shows that these concentrations of NaCl have had 

 no character stic effect either upon the rate of division or upon the 

 size. 



Only in the case of ^^ NaCl was there a slight indication of the 

 modification of the rate of division, this concentration standing 

 on the border line between the injurious and non-injurious solu- 

 tions. In table VII, 100 Paramecia in i^^ NaCl had increased to 

 220, while an equal number in the control had mcreased to but 

 194. In another case, 50 specimens left in 1^^ NaCl for 48 hours 

 had increased to but 64, while in the corresponding control 109 

 had been produced. 



Direct Measurement of Growth after Fission 



Growth in solutions of NaCl was next measured directly by 

 placing in the solutions to be examined specimens that had just 

 divided, as described on page 491. 



.^^^NaCl in hay infusion. The measurements in hay infusion 

 to which NaCl had been added, and in the same infusion without 

 the salt, are given in table VIII. 



TABLE VIII 



Comparative measurements in microns of growing Paramecia in ^^NaCl dissolved in hay infusion, and 



in bay infusion. 



For the first 10 minutes after separation, the halves in the salt 

 solution increased in length at the same rate as the controls, then 

 the length decreased rapidly for 40 minutes, when the Paramecia 

 in the salt had become shorter than they were at the time of sepa- 



