Effect of Chrni/cals on Growth 



495 



control at the beginning had divided, giving seventeen specimens, 

 and the difference in sizes is due to the fact that some of these 

 seventeen specimens are young and not fully grown. I should 

 say however, that the five in the salt were not quite so large as 

 normal. Evidently growth that is almost normal in amount and 

 rate can take place in a fluid that will not sustain life for an\' 

 great length of time. 



The effects in this experiment are explained by the one next 

 performed. The animals were placed in pure distilled water plus 

 a sufficient amount of sodium chloride to make a J^^ solution. 

 The results are shown in Table III. 



TABLE III 



Comparative measurements in microns of Paramecin in ^-^-NaCl dissolved in pure distilled water, and in 



hay infusion 



As the table shows, growth in ^ NaCI took place almost as 

 well as in the hay infusion. At 90 minutes, those in the salt were 

 as large as those in the control. At 5 hours, they had fallen 

 somewhat behind, but at 24 hours they were of about the usual 

 adult size. The lack of food had prevented them from dividing, 

 while 6 of the 21 control specimens had divided, giving 27 alto- 

 gether. The larger average size of the specimens in the salt 

 solution was doubtless due to this division in the hay infusion; 

 some of the specimens in the latter were voung and not full grown. 



Thus a -^^ solution of NaCI in distilled water has the necessary 

 amount of salts for Paramecium to live in it with normal growth. 

 The amount of salts in the -^^-^ solution wasevidently notsufficient 

 to keep the animals alive for a long time. 



