20 



B. mesentericus ruber (Globig). 



Isolated by Globig, 1888 (75), from potato. Described as 

 a slender, motile, bacillus, with oval, very resistant, spores. Gela- 

 tin colonies, round and yellow in the depths; on the surface 

 showing a fringe or halo of fine network, which breaks down in 

 34 days and liquefaction begins. Gelatin stab, funnel shaped 

 liquefaction. Agar colonies are non - characteristic. Agar streak, 

 dirty white and slightly wrinkled growth. On potato a dry growth 

 of a beautiful pink color. Globig described bouillon as clear, 

 with a thick pellicle; my cultures showed cloudiness and pellicle. 

 Litmus milk, curdled and acid. No gas is produced, nitrates are 

 reduced, growth with rose color at 37 C. 



Two cultures from Krdl, 1900, 1903, differed from the above 

 description in not showing spores. Three cultures isolated from 

 the Mississippi River water at different times were used as the 

 basis of this description. 



C. Comparatire and Experimental Study. 



I. Color determination of bacterial pigment 1 ). 



The increasing tendency towards the adoption of definite terms 

 of positive, negative, or quantitative value in bacterial descriptions 

 has not been generally extended to the determination of color 

 produced by bacteria. The pigmentation of an organism still 

 furnishes an opportunity for a more or less lax and undiscrimina- 

 ting nomenclature. Thus, among the red series one whole classi- 

 fication has been made on the basis of such divisions as these : 

 "Pigment carmine", "pigment flesh-colored," "brick-red", "reddish", 

 "rose-colored", "salmon-pink", "yellowish-reddish", "brownish-red", 

 "pinkish", "reddish-pinkish", "blood-red", "red-brick-red". These 

 distinctions may call up well defined color pictures to individual 

 workers, but it is evident that there are difficulties in the way of 

 fitting a new chromogenic organism to such an imaginative scheme. 



In default of a more exact method, statistical biologists have 

 for some time employed a color top 2 ), upon which discs of the 

 primary colors may be arranged, showing sectors of definite pro- 

 portions ; when the top is rotated rapidly the colors blend and give 

 the intermediate tints. Any color may thus be matched, and the 

 percentage of primary colors which go to make it up very closely 

 determined. This method is easily applicable to bacterial colors, 

 and has been adopted in this study. Other color-terms appearing 



1 ) The chemical nature of bacterial pigment, its solubility, and its spectrum 

 analysis has been discussed at length by Schroter (29), Cohn (30), Griffiths 

 (39), Scheurlen (43), Schneider (19), Rosenberg (45), Kraft (49), and 

 others. 



2) The Milton Bradley color top has standard colors of the following wave- 

 lengths: Bed, 656061; orange, 606-611; yellow, 577582; green, 514519; 

 blue, 467472; violet, 419 424. For method cf. Davenport , C. B., Statistical 

 Methods. New York, 1899, p. 9. 



