[BERKELEY] MARINE BACTERIA 19 



(iv) A thin square-ended bacillus occurring in short chains, 

 about 4-5/x. long by -2/^. wide. 



(v) A coccus occurring in small groups, about -Sfi. diam. 

 No, (i) seemed to occur in greatest number. The particles of 

 diatoms, etc., present were covered with bacteria chiefly of this 

 type. 



Twenty and 100 fathom samples. These gave comparatively little 

 deposit on making alkaline and centrifuging. In both cases only two 

 types of bacterium seemed to be present and these in far fewer numbers 

 than in the surface sample. They approximated very nearly to types 

 (ii) and (v) of the above series. 



Cultural Examination 



Since the original intention of this work was to endeavour to 

 isolate denitrifying species of bacteria the only solid sea-water medium 

 available at its start was one designed to that end: Its composition 

 (medium A) was as follows: — 



Calcium Acetate 5-0 grams 



Peptone (Witte's) -2 gram 



Potassium Nitrate -5 gram 



Sodium Phosphate (Na2HP04) -25 gram 



Agar -20 grams 



Sea-water 1000 cc. 



In making up this medium, and all others used in the course of 

 the work, the sea-water used was collected from the shore at a point in 

 the neighbourhood of Vancouver where the density was usually very 

 near to that of the surface sample under examination. The medium 

 was made just alkaline to phenolphthalein after the agar was dissolved, 

 but it developed a slightly acid reaction during sterilization. The 

 precise degree of acidity was not determined. 



Two cultures were made on slopes of this medium from each of 

 the samples of water. In each case one was kept in the incubator at 

 28°C., the other at air temperature (15° to 20°C)^ No growth was 

 obtained at the former temperature in the case of the 20 fathom or 

 100 fathom sample. The surface sample showed a light dotted 

 growth after 43 hours incubation, which appeared to consist of an 

 almost pure culture of a round-ended bacillus about -Sii. wide by 

 1-5 to 2 • 5/z. long occurring most commonly in pairs and in an active 

 state of division. A few thinner round-ended bacilli were also present. 



^ In all subsequent references to "air temperature," a temperature range within 

 these limits is meant. 



