Effect of Chejuicals on Growth 511 



^ NaCl is on the border line; it sometimes decreases growth, 

 sometimes not, dependinig on the conditions. More dilute solu- 

 tions do not effect growth. Young specimens are injured by jo 

 NaCl, while old ones are not. If the parents are subjected to this 

 concentration for a short while before fission, the injury to the 

 young is less. Paramecia can be temporarily acclimatized to a 

 solution that would at first kill them, but after some days in such 

 a solution fission becomes abnormal and ceases and the animals 

 die. The injurious effects of sodium chloride are due partly to 

 increase of osmotic pressure, partly to specific chemical action. 



EFFECTS OF NICOTINE ON GROWTH 



Having studied the effects of the comparatively innocuous sub- 

 stance, NaCl, I now undertook to examine the effects of nicotine 

 (CioHj^Nj). This alkaloid is so poisonous that only minute 

 quantities are required to produce an effect; so minute that the 

 osmotic pressure produced by them is clearly of no importance in 

 the results. The effect of nicotine on single cells is of interest 

 in view of its effect on man (see Lee, Langley, and others). 



Effect of Nicotine upon Adult Paramecia 



One hundred adult specimens of Paramecia taken at random 

 from the stock culture were put into watch glasses containing 

 known amounts of nicotine dissolved in hay infusion. These 

 were allowed to remain for 50 hours. The results are given in 

 table XVII. 



From this table it is clear that strengths of nicotine from 1-1,000 

 up to 1-20,000 kill adult Paramecia in different times varying 

 from 2 hours to 50 hours. Those in the 1-40,0000 solution and 

 the more dilute solutions continued to live. In order to determine 

 whether there was any effect upon the size a number of specimens 

 were taken from these solutions, killed, and measured (see table 

 XVIII.) 



