148 G. HAROLD DREW. 



room temperature averages 29*5° C. After about eigliteen hours 

 the colonies are well developed, they are white in colour, circular, 

 but with finely irregular outline, and have a granular appearance. 

 Superficial colonies are much elevated at first, but as growth pro- 

 ceeds, spread rapidly over the surface of the Agar. The deep 

 colonies remain small, circular, and discrete. Growth is somewhat 

 more rapid on the Peptone Agar than on the Potassium malate 

 Agar, and the older colonies develop a brownish tinge in the centre 

 when growing on the former medium. 



On Gelatin Peptone (5 per cent Peptone, kept at between 20° 

 and 25° C. to ensure the medium remaining solid) growth was very 

 slow ; in stab cultures growth proceeded slowly from the surface 

 downwards, forming a funnel-shaped depression of liquefied 

 gelatin. Acid formation occurs in Glucose, Mannite, and Cane- 

 sugar, but not in Lactose media. 



Growth is totally inhibited at a temperature of 10° C, but takes 

 place slowly at 15° C. 



Growth is much retarded by exposure to bright sunlight, but the 

 bacteria are not killed by a ten hours' exposure. 



The bacteria are facultative anaerobes, but growth under anaerobic 

 conditions is very slow. 



In Gran's medium growth and denitrification are rapid, but no 

 growth occurs if the Potassium nitrate be omitted, or if the 

 Calcium malate be replaced by Calcium carbonate. Growth in a 

 pure solution of Peptone in sea-water is very slight, but becomes 

 abundant if Potassium nitrate be added, when denitrification quickly 

 ensues. 



In its cultural reactions this bacterium is very similar to certain 

 denitrifying forms found in the English Channel. The chief points 

 of difference consist in its much greater denitrifying power, and 

 the higher temperature necessary for its growth, by which it 

 would be prevented from spreading into colder waters. 



The characteristics of the scarcer, non-denitrifying, form of bacterium 

 found on the Peptone Agar plates made from surface samples are as 

 follows : — 



Growth on the Potassium malate Agar medium is very slow and 

 indefinite. On Peptone Agar growth is somewhat slower than in 

 the case of the denitrifying form. On the surface, circular cream- 

 coloured colonies are formed having a brownish centre, the edges 

 are smooth and regular, and the colony remains discrete and 

 does not tend to spread over the surface. The deep colonies are 



