[BERKELEY] MARINE BACTERIA 31 



this was it that reinoculation was repeated several times into larger 

 volumes of the medium and in every case the same peculiar appearance 

 developed. The similarity may have been mere coincidence, but it 

 seems quite probable that the appearance in the sea was due to some 

 large mass of organic material undergoing bacterial decomposition. 

 It is significant in this connection that only a few days previously, 

 at spots not far distant from that at which the sample was taken, 

 the surface tow-net had brought up solid hauls of practically pure 

 cultures of Ctenophora. A test of one of these surface water cultures 

 in the Peptone medium showed copious ammonia production after 

 2 days. Microscopic examination of the culture showed an appar- 

 ently pure growth of an actively motile round-ended bacillus about 

 • 5fi. wide and 1 • 5 to 2 • 5^. long in an active state of division. 



The cultures kept at air temperature all showed growth in 3 

 days. The culture from the surface sample the strongest, the 20 

 fathom sample rather less and the 100 fathom sample least. The 

 culture from the surface sample had, however, not developed the 

 peculiar flocculent precipitate formed at 28°C; the medium was 

 uniformly turbid and a thick scum had formed on the surface. All 

 showed the presence of ammonia, the surface culture more strongly 

 than the others. 



All the cultures showing growth were plated on a medium con- 

 sisting of the -2 per cent Peptone sea-water with 2 per cent of Agar 

 added. The reaction of this medium was less acid than -\--5 (i.e. 

 contained less than -5 per cent normal acid) and was therefore not 

 neutralized. As in the previous cases no growth was obtained on the 

 plates from the 20 fathom and 100 fathom samples. From the cultures 

 from the surface sample the following types of colony were obtained 

 and subcultures made from one of each on to slopes of the same 

 medium: — 



(i) Small, round, cream-coloured, flat, smooth surface, entire 

 edge (Culture X). 



(ii) Like (i), but white and spread (Culture XII). 



(iii) White, flat, round, finely granular surface, slightly un- 

 dulate edge, dry and adherent to medium (Culture XIV). 



(iv) Like (iii) but smaller (from different plate) (Culture XV). 



Inoculations were also made into a 2 per cent solution of Casein in 

 sea-water from the surface sample in order to test the power of am- 

 monia formation from a more complex nitrogenous compound than 

 Peptone. Ammonia was formed in quantity after 3 days incubation 

 at 28°C. 



Sec. V, Sig. 3 



