The Relatìons between Marine Animai and Vegetable Life. 371 



ammonia has beeu reached, for after an additional 29 days no further 

 purificatioD resulted. The degree of puritìcatiou seems to bave beeu 

 practically the same for ali three waters. 



This very marked purification of water kept in darkness ìs, we 

 must conclude, almost entirely due to bacterial action. Thus some 

 of the same Aquarium water, kept under the same conditions as the 

 above, but to wbich .1% of corrosive sublimate had been added, 

 was found on analysis after "2G days to contain .255 mgm. of free, 

 and .120 mgm. of organic ammonia, or respectively 25^ and 11^ 

 less than the originai water. This diminutiou was probably due to 

 the Vaporisation of some of the ammonia from the water, and to 

 coagulation and partial fixation of the proteids in the organisms 

 present in the water, which on distillation would otherwise bave 

 evolved some ammonia. 



Stili two other jars of water were kept in absolute darkness 

 under conditions similar to the above. One of these jars contained 

 Aquarium water which had beeu heated to boiling point in a corked 

 flask, and then cooled rapidly, so that practically none of the am- 

 monia contained in it esca]>ed. The analyses were as follow: 



Free NFIa Organic NH3 



Originai water, after heatiug .350 mgm. .202 mgm. 

 After 26 days .218 .125 



- 54 - .020 .090 



Here we see that after a period of 26 days, which was sufficient 

 in the other cases for the maximum purification of the water to be 

 effected, only a small proportion of the ammonia was removed, and 

 that even after 54 days the limit of purification was not reached. 

 This delay in the purification was obviously due to the bacteria in 

 the water having been killed off by the beat. The water had been 

 poured into an unsterilised jar, receutly washed out with sea-water, 

 hence there were doubtless sufficient bacteria preseut which could, 

 on subsequent multiplication, exert their purifying action. 



The other jar kept in darkness was also filled with A(|uarium 

 water, but the jar itself contained a layer of green and purple brown 

 alga3 graduai ly deposited on it from Aquarium water after it had 

 stood for 36 days in diffuse light. After 26 days in darkness, this 

 layer of algse had diminished in amount, whilst the water itself was 

 found to contain .007 mgm. of free, and .126mqm. of organic ammonia, 

 or respectively 98^ and 1% less than the originai water. As we 

 bave already seen, the organic ammonia in water kept in diffuse 



