337 



the cell-wall, which slime may spread through the liquids, and makes the indivi- 

 duals of the colonies on agarplates cohere into one tough mass. From B. Kic- 

 liensis was even a variant obtained whose colonies appear on the agar plates as 

 a very consistent, almost dry zoogloea, but the analogous variant did not till 

 now arise from the common prodigiosus. The viscosus (6), derived from the latter, 

 is an ordinary red slime bacterium. 



This red-coloured, tough-slimy form, which may be called B. prodigiosus 

 viscosus, is no doubt a plus-variant. Its production has been observed under the 

 most different nutritive conditions, between the temperatures 10 (in a cellar) 

 and 30 C., but always and exclusively in liquid media, never on a solid one. 

 The latter circumstance is apparently the reason why the numerous experimenters, 

 who have studied B. prodigiosus, have not seen this variant. It is true that 

 Scheuerlen 1 ) observed that old /ra//g/Vwtf-cultures sometimes turn slimy, but 

 he ascribed it to their becoming alkaline and overlooked that a new constant 

 form was produced. 



The only distinct condition which seems different in the liquid cultures 

 compared with the solid, is the access of oxygen. In the depht of the liquid this 

 access must, of course, be very deficient for a long time, or even be entirely 

 lacking, as the upper layers of the culture, which are rich in bacteria, take up 

 all the oxygen. Consequently anaerobiose becomes possible in the depht, which 

 is not the case in cultures lying free on a solid medium, and this partial an- 

 aerobiose is apparently the stimulus which induces the formation of the slime 

 variant. That here a rather complex influence and not a direct action must be 

 ascribed to the partial withdrawing of the oxygen, follows from the fact that 

 the culture of B. prodigiosus at complete exclusion of air, as in a closed bottle, 

 does not, even with repeated transports, give rise to the slimy variant. At tem- 

 peratures of about 35 C. this variant is no more formed, although the growth 

 of prodigiosus is then still very strong; at 37 the growth slackens or ceases en- 

 tirely, according to the food. 



In the following liquid media the production of the slime variant has with 

 certainty been observed, as well after repeated re-inoculations as after prolonged 

 keeping of one and the same culture at 25 to 30 ^ C. : in broth, in broth with 

 i pCt. of glucose, in malt-wort, in tap-water with 5 pCt. of pure gelatin and 0,02 

 pCt. KaHPOi, and in tap-water with 2 pCt. of glucose, 0.5 pCt. of asparagine, 

 0,02 pCt. KaHPOi, always cultivated at 30 C. and with repeated transports after 

 two days or longer. From this we also recognise that there is no question of 

 a direct influence of the food on the production of the variant. 



The auralus- and hyalinus- variants, also, have only taken rise in liquid cultures, 

 namely in broth and in the glucose-asparagine solution. Moreover, hyalinus, which 

 is of a deep vine red, is easily obtained from a solution of pure gelatin in tap- 

 water with 0.02 pCt. K2HPO4, after repeated re-inoculations, at 30'* C., whereby 

 also hyalinus viscosus results. 



The colourless or white variants, which only differ from the original form 

 in producing no pigment, should certainly be considered as minus-variants. They 



') Archiv fur Hygiene. Bd. 26 p. i. 

 M. W. Beijerinck, Verzamelde Geschriften; Vierde Deel. 22 



