150 



JOSEPH HALL BODINE. 



scope. The fatal exposure was taken at that time when approxi- 

 mately one half of the larvae were killed, i.e., when movements of 

 the heart and alimentary canal ceased. Many cultures were 

 used in experiments and slight variations in their resistance were 

 shown but in the following only average results will be given. It 

 is, however, of some interest to note that in practically all the 

 cultures from which larvae were obtained the hydrogen ion con- 

 centration showed them to be neutral or slightly alkaline in 

 reaction (P H : : 7.0-7.4). The chemicals used were, hydrochloric, 

 acetic, oxalic, butyric, salicyclic and carbonic acids and mercuric 

 chloride. 



FATAL EXPOSURES IN MINUTES TO DIFFERENT STRENGTHS OF ACIDS (TEMP. 25 C.). 



From the above table showing the length of life in minutes of 

 larvae in various strengths of acids it is evident that the animals 

 are able to withstand abnormally high concentrations of acids 

 for rather long periods of time. This remarkable resistance of 

 mosquito larvae is more strikingly shown when compared with 

 that found for other forms e.g., Honda (6) found that the free- 

 living nematode Rhabditis elegans withstood o.oi normal HC1 

 for 60 minutes, Daphnia for 23 minutes, tadpoles for 12 minutes 

 and paramecium for I minute. (Personal communication to be 

 published in Journal of Experimental Zoology.} MacArthur (7) 

 found that Planarians are killed in a very short time by exposure 

 to HC1 of P H 2-4.5. It has also been found by the author (8) 

 that cysts of Colpoda withstand o.ooi N HC1 for a strikingly 

 long time. 



That the hydrogen ion concentration is not necessarily the 

 only factor in the toxicity of acids for larvae is shown by compar- 

 ing the effects of a saturated solution of CO 2 in H 2 O of a P H of 

 approximately 3.7 with a solution of HC1 of the same PH value. 



