IN WATER CONTAINING FREE ACIDS. 187 



appearance. Acid was again added till the total acidity 

 had reached 0*153 grm. per litre. The appearance now 

 presented was similar to the former, except that life was 

 still more languid, and after an hour all had ceased. The 

 whole solution presented the appearance of being filled with 

 decomposed and decaying organic matter floating about in 

 shreds. Thinking that perhaps the length of time which 

 had elapsed since the Rotifers had been obtained might 

 have had some effect, a portion of the original solution 

 which had been kept apart for the purpose, but to which 

 no acid had been added, was examined, and the life found 

 to be as active as at its first origination. 



A number of experiments were also made in order to 

 see what amount of free acid would prevent the origination 

 of life. In the above case it was seen that 0*065 grm. per 

 litre did not prevent it, that being the original acidity of 

 the liquid. The amounts given below were then tried with 

 the following results : — 



Time allowed to stand. Total acidity. Kemarks. 



days. grm. per litre. 



g 0*070 Life abundant. 



20 o"o74. Little or no life. 



26 o*o8o No life. 



Here, then, we see, the line of demarcation is distinctly 

 marked, 0*004 grm. per litre making a very decided im- 

 pression on, if not completely stopping, the origination of 

 life, and o*oi grm. per litre entirely preventing it. 



The next acid tried was hydrochloric acid. The same 

 amount of air was taken and treated in a similar manner, 

 the acidity in this case amounting to 0*0085 g rm « per litre, 

 calculated as hydrochloric acid. 



This, after being left for five days under the same con- 

 ditions as formerly, was very full of life and in active 

 condition. 



