26 Papers from the Marine Biological Laboratory at Tortugas. 



peptone in sea-water and kept at between 20° and 25° C. to insure the 

 medium remaining solid), growth was very slow; in stab cultures growth 

 proceeded slowly from the surface downwards, leaving a funnel-shaped 

 depression of liquefied gelatin. 



Acid formation occurs in dextrose, laevulose, mannite, and cane sugar, 

 but not in lactose media. 



Growth is 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 10 hours' exposure. 



The bacteria are facultative anaerobes, but growth under anaerobic 

 conditions is very slow. 



In Gran's medium growth is rapid, but no growth occurs if the potassium 

 nitrate be omitted, or if the calcium malate be replaced by calcium carbon- 

 ate. 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. The most rapid growth was produced in sea-water con- 

 taining 2 per cent peptone, i per cent potassium malate, and 0.5 per cent 

 potassium nitrate, and in this clear medium a slight floccular precipitate, 

 presumably of calcium salts derived from the sea- water, was soon formed. 

 Growth was also rapid at first in a solution of 5 per cent potassium malate 

 and 0.5 per cent potassium nitrate in sea-water, but growth apparently 

 ceased in this medium after a few days and denitrification was never com- 

 plete ; a slight precipitation occurred and the solution was found to have very 

 definitely increased in alkalinity. 



This bacterium does not appear to have been previously described, and 

 I propose for it the name of Bacterium calcis, owing to its power of pre- 

 cipitating calcium carbonate from solutions of calcium salts. This point 

 will be dealt with later in the paper. 



The characteristics of the scarcer non-denitrifying form of bacterium 

 found on the agar plates are as follows : 



Growth on the potassium malate agar medium is very slow and indefi- 

 nite. On peptone agar growth is somewhat slower than in the case of the 

 denitrifying form. On the surface, circular cream-colored colonies are 

 formed, having a brownish center; the edges are smooth and regular, and 

 the colony remains discrete and does not tend to spread over the surface. 

 The deep colonies are smaller and usually ovoid in shape, and of a somewhat 

 darker color than those on the surface. 



No growth was obtained on gelatin media. 



Acid formation as shown by the neutral red reaction occurs in dextrose 

 and laevulose, but not in cane sugar, lactose, or mannite media. 



Growth takes place slowly at 10° C. No visible growth occurred at 0° 

 C., but cultures were not killed by 24 hours' exposure to this temperature. 



Growth is retarded by light, and cultures are killed by 4 hours' exposure 

 to bright sunlight. 



The bacterium is a strict aerobe. 



