43 



4) Considerable nonnal variation in biological characters is 

 seen among the members of the Pro digios us group on ordinary 

 media. In many cases this does not exceed the variations shown 

 by a series of inoculations made from the same culture. It was 

 noticeable that although gas production varied for most of these 

 organisms, the ratio of C0 8 to the total gas remained comparatively 

 constant. 



5) Within comparatively narrow limits the pigment color of the 

 Prodigiosus group may be altered by changing the composition 

 of the nutritive medium. 



6) Also by variation in the composition of the nutritive medium, 

 cultures usually distinct from one another in pigment character can 

 be made to approximate, e. g. to change from orange to violet 

 red; or to assume pigment qualities previously foreign to them, 

 e. g. metallic luster. The former characters are regained upon 

 transference to the original medium. 



7) There is a tendency to violet red pigment in more acid, to 

 orange red in more alkaline media. 



8) Dextrose and saccharose in peptone agar medium favor 

 pigment formation much more than does lactose. 



9) The ability or non-ability to produce pigment in non-proteid 

 media is a particularly constant character for each of the different 

 members of the Prodigiosus group; but strains which are 

 otherwise approximate in biological characters may differ in this 

 ability. 



10) Two strains in the Prodigiosus group, viz. B. ruber 

 in die us I and II, differed from all the others in the ability to 

 produce pigment in pure asparagin solution, without MgS0 4 or 

 K 2 HP0 4 . 



11) The effect upon pigment production of adding dextrose and 

 saccharose to a standard asparagin solution is similar to that of 

 concentrating the solution by increase of asparagin content. Here 

 again, lactose is shown to be without effect upon pigment. 



12) There is probably little or no correlation between luxuriance 

 or vigor and the power of pigment formation. Hence pigment 

 production does not appear to be essential to the life-processes of 

 an organism. 



I). Notes on Groups of Bed Chromosome Bacilli. 



The division into groups of the pigment bacteria by means of 

 the color scale falls in closely with the division according to other 

 biological characters as shown by the species description table. 

 Aside from the differentiation made in the discussion of pigment 

 production above, the inter-relationship of the members of some 

 groups may be briefly described as follows: 



