The Relations between Marine Animai and Vegetable Life. 405 



when other but unheated specimeus of water contained on aa average 

 only .012 nigra. ì^2^:\ì this specimen contained l.OSOmgm., or ninety 

 times as much. 



Vegetable life other tlian bacterial seems as a mie to slightly 

 increase the i)roportion of nitrites present. Thus a water which before 

 filtration through sand impregnated with diatoms and algfe contained 

 .054 mgm., after it contained .067 mgm.; another specimen, .100 mgm. 

 before, and .135 mgm. after. Another specimen, which had been 

 fìltered very slowly through Aquarium sand (1 litre in 80 miuutes), 

 contained .693 mgm. after larvju had been allowed to grow eight 

 days in it, whilst water filtered rapidly through the same sand 

 (1 litre in 4 minutes), contained only .045 mgm. after the larvai growth. 

 The normal larvai water contained .100 mgm. Again, a specimen 

 of water kept 35 days in diffuse light, whereby it was subjected to 

 the action of diatoms, contained .108 mgm. of N2O3. Stili again, 

 water in which .6 gm. per litre of the red weed Gelklium had been 

 left live days, contained .360 mgm., and water to which was added 

 .7 gm. per litre of Gelidium with founds of Viva attached to it, con- 

 tained after eight days larvai grow^th .630 mgm., as against the 

 .450 mgm. of N2O3 present in normal larvai water. 



The growth of larv« in a water seems generally, but not always, 

 to increase the proportion of nitrites. Thus after eight days' growth 

 in normal water, the increase was found in two cases to be from 

 .054 and .070 mgm. to respectively .100 and .495 mgm. This increase 

 probably depends chiefly upon the amount of organic impurity 

 originally present in the water, and is but little atfected by the 

 larvai metabolism itself. Thus open sea-water, which originally con- 

 tained .022 mgm. of N2O3, after eight days' larvai growth contained 

 only .036 mgm. That it is the organic impurity present, rather than 

 the amount of available ammonia, is shown by an experiment in 

 which .0394 gm. of ammonium chloride was added to the water. 

 After eight days' larvai growth, this water contained .108 mgm N2O;;, 

 as against the .100 mgm. present in the normal water. The amount 

 of nitrification varies considerably in different cases, it probably 

 depending upon the number of nitrifyiug organisms in the water. 

 Thus in Expts. 97 to 104 inclusive, the various specimens of water 

 contained on an average .087 mgm. N2O3 after eight days' larvai 

 growth. In Expts. 120 to 129 they contained on an average .140 mgm., 

 but in Expts. 130 to 138 no less than .322 mgm. This considerable 

 increase in the amount of nitrites was present in every experiment 



Mittheilungen a. d. Zool. Station zu Neapel. Bd. 13. 27 



