138 CHROMOPAROUS BACTERIA. 



air only, is, according to the researches of this observer, at first 

 diffusely distributed through the young cells. It is then excreted, 

 and collects into various-sized granules which lie between the cells 

 and so impart a red coloration to the culture. The tone of the 

 colour changes with the age of the culture, beginning as a pale 

 rose and passing through a bright scarlet stage into dark brown- 

 red. According to the researches of J. SCHROETER (I.) and 

 SCHEURLEN (III.), the colouring matter is insoluble in water, but 

 readily soluble in alcohol, xylene, chloroform, carbon bisulphide, 

 and, to a slighter extent, also in ether and in fats (e.g. olive-oil). 

 The alcoholic solution exhibits in the spectroscope three ab- 

 sorption bands: one beyond D, the second just before E, and the 

 third before F. The elementary formula was determined by 

 A. B. GRIFFITHS (I.) as C 3S H 56 N0 5 , though the analytical results 

 obtained by Scheurlen are not in conformity therewith. The 

 opinion expressed by 0. ERDMANN (I.) that the colouring matter 

 generated by M. prodigiosus is identical with fuchsine has been 

 contradicted by OTTO HELM (I.) and BORDONI-UFFREDUZZI (I.). 



This fission fungus forms a very suitable object for the study 

 of mutability. E. WASSERZUG (I.) traced the changes of form 

 which this species underwent in consequence of alterations of the 

 conditions of nutrition. By repeated cultivation on faintly acid 

 media 0.3 to 0.4 grm. of tartaric acid per litre cultures are 

 obtained the cells of which are no longer globular or oval, but 

 exhibit the form of actively motile long rods and threads ; the 

 modifications being the more pronounced as the number of inocu- 

 lations is increased. As soon, however, as an inoculation is made 

 from such acid liquids into an alkaline medium, the typical short 

 cells reappear. This reversion also occurs when the cells remain 

 for some time in the original acid medium, after the reaction has 

 become alkaline from the transformation, products (trimethylamine, 

 &c.) excreted by the microbe. 



In addition to the form of the cells, the development of colour- 

 ing matter is, as Schottelius has found, also dependent on the 

 nutritive conditions; since, if a prodigiosus culture, grown at 

 io-25 C. and already red in colour, be inoculated on sterile 

 potatoes (steamed and cut in halves), and the temperature kept at 

 3 8 -39 6., the inoculating streaks develop into colourless streak 

 cultures. From these again a red culture can be once more 

 obtained by suitably modifying the conditions of the culture, i.e. 

 reverting to a lower temperature. 



88. Lipoehromes. 



With the organism mentioned in the last paragraph are classi- 

 fied a number of other species also producing red colouring matter. 

 One of these, Bacillus erythrosporus, first discovered by ED. EIDAM 

 (I.) in putrefying egg-albumin, is of particular interest. This is a 



