16 THE ROYAL SOCIETY OF CANADA 



recombining it. No evidence of the existence of such organisms has 

 yet been brought forward. In temperate seas, on the other hand, 

 this reduction of nitrates takes place very little, if at all, and the 

 nitrogen remains in combination dissolved in the water and available 

 for subsequent assimilation. Drew isolated a particular species of 

 denitrifying bacterium to which he attributed the loss of nitrogen in 

 tropical seas {Bacterium calcis — Drew; Pseudomanas calcis — Keller- 

 man &. SmithO and observed incidentally that the reduction of the 

 nitrate by the organism was accompanied by the precipitation of 

 calcium carbonate from the calcium salts dissolved in the water. 

 He suggests that the chalky mud flats forming the great Bahama 

 Banks, and those which are found in places in the neighbourhood of 

 the Florida Keys, are being precipitated by the action of Bad. calcis 

 and that the same organism may have been an important factor in 

 the formation of chalk and oolite rocks elsewhere. 



A number of references will be found in Drew's paper to previous 

 work on marine bacteria considered both generally and in particular 

 regard to denitrifying, nitrogen fixing, and nitrifying species, but in 

 nearly all the cases quoted here and in the papers to which I have had 

 access, the authors seem either to have been content to isolate and 

 describe types without considering their chemical activities or to have 

 dealt with species collected in inshore waters where the conditions 

 would not be comparable with those existing in the open sea. 



The original object of the work to be described was to ascertain 

 whether the water in the open sea in the neighbourhood of Vancouver 

 contained bacteria capable of bringing about denitrification in simple 

 culture media containing nitrates and, if so, if Drew's Bad. calcis 

 could be isolated from it, but in its subsequent development its scope 

 was widened to include an examination for ammonifying, nitrifying 

 and nitrogen fixing bacteria. 



Sampling 



The samples of water on which the work was carried out were 

 taken on August 27th, 1917, at a point about 3 miles due east of 

 Nanaimo, Vancouver Island. It was hoped that this point was 

 sufficiently far from land to provide water in which land or littoral 

 forms of bacteria might be expected to be absent but the conditions 

 were not oceanic owing to the effect of the fresh water from the Fraser 

 and other rivers. The density of the surface water was, for instance, 

 only 1-0171 (corrected for 15°C). It seemed, however, sufficiently 



1 Kellerman & Smith, Journal of the Washington Academy of Science, Vol. IV, 

 No. 14. 



