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A Table showing certain Cultural Characteristics of 

 some of the Commonest Bacteria found in the Labora- 

 tory Tanks at Plymouth. 



By 

 G. Harold Drew. 



The following table is merely intended as a rough classification of eight 

 of the most common species of bacteria found in the Laboratory Tanks. 

 Only the forms which occur free in the water in the greatest numbers 

 have been considered, and the moulds and higher bacteria which can be 

 cultivated from scrapings from the walls of the tanks have not been 

 included. 



Until further and more detailed work has been done on the subject, 

 it seemed better to designate the various species by numbers instead 

 of names, since the majority have probably not previously been 

 described. 



The culture media employed were similar to those ordinarily used 

 for bacteriological work, with the exception that fish broth (made from 

 dogfish) was substituted for meat broth, and that sea-water was used in 

 place of tap-water. All media were faintly alkaline to Neutral Eed. 



The medium designated as " Gran's medium," has the following com- 

 position : — 



Sodium chloride . . . . .8-8 grammes. 



Potassium nitrate . . . 0'25 ,, 



Sodium phosphate (NaoHPO^, 12 H^O) 0-125 „ 



Calcium malate . . . .in excess of its solubility. 



Distilled water ..... 2.50 c.c. 



and is fully described by H. H. Gran in the Beiycns Museums Aarhog, 

 No. 3, 1901. 



The sample of water, from which the bacteria classified in the taljle 

 were isolated, was collected from just below the surface of one of the 

 tanks in the upper Laboratory at 5.30 p.m. on December 6th, 1909. 

 01 c.c. of this sample plated on Fish-broth, Peptone Agar at 30° C., gave 

 an average of 130 colonies of all kinds. Samples collected on other 

 occasions show that the eight species described below may be considered 

 as always present and abundant in the tank water. 



