The Relations between Marine Animai and Vegetable Life. 



373 



witli sea-water, iu that they were made in the presence of light. 

 Thus Uffelmann has shown* that these bacteria may oxidise the 

 ammonia in the water, more or less irrespective of the presence of air. 

 Heraeus has shown^ that some kinds of bacteria exert an oxidisiug 

 action, and others a reducing one. Again, S. Leone, who worked 

 with distilled water containing a little gelatin, found that the organic 

 substances were gradually decomposed into inorganic Compounds, first 

 ammonia, then nitrous acid, and then nitric acid, beiug in turn formed ^. 

 This subject of nitrification, with reference to sea-water, will be 

 discussed in this paper further on. 



It was remarked, whilst diseussiug the second series of the 

 above experiments, that the purification of the water appeared to 

 reach its limiting value after 25 days. The three specimens of water 

 (Aquarium water, filtered water and ,seeded' water), then contained 

 respectively .007, .008 and .005 mgni. of free ammonia per litre, and 

 .065, .069 and .059 mgm. of organic ammonia. It was thought to 

 be of interest to determine what relation pure open sea-waters bore 

 iu their composition to these bacterially puritìed waters, so the 

 following analyses were made. 



These analyses show that open sea-water practically reaches its 

 limiting degree of purity at about 3 kilometres from the shore, and 

 also, that this degree of purity is practically the same as 

 that which was in some cases effected in Aquarium tank 

 water by bacterial action in the darkness. This is a 

 significant fact, as it seems to show that by merely keeping impure 

 water for a few weeks in darkness, as great a degree of purity 

 may be reached as is found in the open sea, where the water is 



1 Arch. Hyg. 4. Bd. II. 1. 



2 Zeit. Hyg. 1. Bd. pag. 193. 



3 Gazetta Chimica Italiana. 1887. 



Mittheilungen a. d. Zoolog. Station zu Neapel. Bd. 13. 



25 



