338 



are obtained with more ease than the slime variants and, at least as to N 4 ; 

 have also been detected by other authors 4 ). 



Except under the said conditions, apt to keep them constant, all the cultures 

 as well in liquid as on solid media, vary sooner or later towards white. The 

 original form does remain preserved, but a colourles variant is thrown off, which 

 is still more constant than the stock itself. 



Not always does one and the same variant result in this case: two unco- 

 loured constant forms, N 4 and 5 can easily be distinguished if they originate 

 at the same time, and their colonies are on the same agarplate so that they may 

 be compared somewhat magnified. One, albus hyalinus, then looks more blueish 

 transparent, the other, albus, is more of a cloudy and opake white; under the 

 microscope the former proves to consist of smaller cells than the latter. 



The cause of the production of white variants cannot be a more or less 

 abundant access of oxygen, but must probably be sought in a stimulus, exerted 

 by secretion products which remain enclosed in the interior of the cells. 



Although the presence of ammoniumcarbonate in the medium (broth-agar), 

 as also cultivation at temperatures higher than 30 C. e. g. at 33 C., prevent 

 pigment production, no hereditary variation at all is caused by these influences. 

 If the thus treated colourless cultures are transported at 20 to 25, no white 

 variants are obtained from them, but the normal form is found back unchanged, 

 if at least the above mentioned precautions to preserve the constancy of the 

 stock are not neglected. 



When the white variants of the normal form are cultivated at 30 C. in 

 bouillon or in malt-wort, the cultures will, after a few re-inoculations, turn slimy 

 like those of the red normal form itself. Colony culture on bouillonagar proves 

 that white slime variants are thrown off, in the same way as the normal form 

 throws off the red ones. The white slime variants (N. 7 ? and 14) correspond 

 by the nature of their colonies to the two white forms, albus (4) and ailnis hyalinns 

 (5), considered above. 



There is still another method to obtain the colourless slime variant from 

 the red one. If this latter is cultivated at 30 in malt-wort or in bouillon, we 

 find after one or two transferrings, each time after two days, and when sown 

 on bouillon-agar, many white slime colonies together with the unchanged red, 

 moreover a considerable number of quite normal, not slimy red colonies, X". i i 

 which is to be considered as atavism, but an atavism reposing on the loss of a 

 character. The white slime variant, thus obtained by minus-variation, and found 

 in the table as N. 7, seems identic with the one produced by plus-variation from 

 the not slimy white variant, which latter for that reason has not been specially 

 mentioned. 



Already in my earlier paper I spoke of rose variants, which so to say, keep 

 the middle between the normal form and the white variant. They may be pro- 

 duced in various ways, for instance, by cultivating the normal form on plates 

 of pure gelatin dissolved in distilled water (H2O, io/ of gelatin) at room tem- 



l ) In Lehmann and Neumann's Atlas 4*h Ed. 1907, Table 30, Fig 3, shows a 

 coloured image of a pure culture* of prodigiosus, consisting of red and white colonies. 



