[BERKELEY] MARINE BACTERIA 35 



(c) The same as (b) with addition of the following salts to 

 make it more nearly the same composition as sea- water: — 

 magnesium chloride -36 per cent, magnesium sulphate -23 per 

 cent, calcium sulphate -14 per cent, potassium chloride -076 per 

 cent. 



(d) Sea-water. 



■ The other constituents of the media were: — 



"Lemco" -3 percent 



Peptone (Witte's) -5 per cent 



The media were not neutralized since their reaction after boiling 

 was less acid than 4- -5. 



The cultures were kept at air temperature for a week to ten days. 

 Those showing no growth after this period were reinoculated and kept 

 at 28°C. 



None of the cultures in the (a) medium showed any growth at 

 air temperature. Only No. XXVIII grew at 28°C. 



In the {b) medium Nos. I, VI, XII, XIX, XXVII, XXVIII, 

 showed growth at air temperature. No. X grew only at 28°C. All of 

 these showed only a weak growth as compared with that obtained 

 in sea-water broth and the remainder failed to grow at all. 



In the (c) medium all the cultures grew at air temperature except 

 Nos. XII and XXVII, which grew at 28°C, and Nos. Ill, VI.I, XV and 

 XXII, which failed to grow at all. 



In the (d) medium, sea- water broth, all the cultures grew at air 

 temperature. The cultures showed considerable variation in vigour 

 of growth some forming a thick scum and heavy precipitate, others 

 little more than a turbidity. This is indicated in the summary of 

 growth characteristics at the end of this paper by the figures 1, 2 and 3 

 respectively, 1 indicating a very strong growth, 3 a very slight one 

 and 2 an intermediary degree. Hanging drops of the culture were 

 examined as soon as growth was apparent and the degree of motility 

 of the organisms present recorded in the same way, 1 indicating a 

 highly motile form, 2 a slightly motile one and 3 an absence of motility. 

 Films from each culture were also prepared and examined. 



Precipitation of Ammonium Magnesium Phosphate. 



In all of the cultures (except Nos. XXII and XXVII) in both 

 artificial and natural sea-water broth, a crystalline precipitate, of 

 which the individual crystals were easily visible to the unaided eye, 

 formed after two or three weeks. The crystals were easily separated 

 by centrifugalizing the culture? and were found to consist of ammonium 

 magnesium phosphate. A solution of "Lemco" invariably contains 



