develop especially in dilute media at the side of the common bacteria, the most 

 different food may be used for the first part of the experiment. 



So, an agarplate, only containing some potassiumfosfate and ammoniumsulfate, 

 was sprinkled with a little dry inulin mixed with garden soil. The soon developing 

 flora was washed off under the tap by which the loosely adhering bacterial colonies 

 together with the non-decomposed inulin, were removed. The agarplate was now 

 clear again but in the surface were hundreds of Actinomyces colonies which had not 

 been removed by the washing, as they had penetrated too deep into the agar. After 

 treating with the tyrosin solution in which he melanin bacterium was suspended and 

 a renewed cultivation for some days at 30 C., black melanin spots appeared around 

 some six colonies of Actinomyces; this species must thus be rather common in 

 the soil. 



The tyrosin Actinomyces can also very easily be isolated from the roots of the 

 clmtree (Ulmus campestris), in whose dead periderm cells an almost pure Actino- 

 myces flora occurs, as I demonstrated before 1 ). For the development of this flora 

 some of the hairroots are carefully washed, to remove the adhering soil and are then 

 ground in a mortar. The thus obtained brown paste is diluted with water, mixed 

 with the tyrosin bacterium (which however is also rather common on the elm roots 

 themselves), then sown out on a tyrosinplate of the above composition. After a few 

 days numerous colonies of Actinomyces develop at 30 C., among which some jet- 

 black ones. 



Here it should be called to mind that the two organisms produce no pigment on 

 peptone or broth-containing media, neither each for itself nor in combination. But 

 herefrom cannot be concluded that at their cultivation from peptone no tyrosin ori- 

 ginates. Nevertheless the conclusion must be drawn, that if at the splitting of the 

 peptone tyrosin is indeed formed, it is oxidised in another way but not to melanin. 



That this Actinomyces must belong to another species than Actinomyces 

 cliromo genes, so common in our environment, is obvious. The latter namely is 

 characterised by the production of a dark brown pigment from pepton, (but not from 

 tyrosin) in which, as I have formerly 2 ) shown, under certain circumstances chinon 

 may be found. 



Several other species of Actinomyces produce blue, red, or yellow pigments, 

 whereby, as to the blue and red, the simultaneous presence of certain varieties of 

 hay bacteria is favourable. In this case it is not tyrosin, but glucose, malates and 

 nitrates that form the chromogeneous food, so that the symbiose is then evidently 

 associated with other factors than those active in the production of melanin from 

 tyrosin. 



Hitherto I have not yet been able in liquid cultures with the help of Actino- 

 myces and its symbiont to produce a somewhat considerable quantity of melanin. 

 This could not be foreseen as this genus is as common in the mud of moats and canals 

 as in garden soil. But some experiments as the above to find our Actinomyces in 

 mud gave no result, so it seems that this species at least is a real inhabitant of 

 the soil. 



') Centralbl. f. Bakter. 2. Abt. Bd. 6, S. 2, 1900. Arch, Need. 1900, p. 327. 

 2 ) Centralbl. f. Bakter. 2. Abt. Bd. 6, S. 2, 1900. Arch. Neerl. 1900, p. 327, Commonly 

 the chinon is absent, which I did not know in 1900. 



M. W. B eijeri nc k, Verzamelde Geschriften ; Vijfde Deel. 



' 



