( 157 ) 
Very characteristic also is the growth of this bacterium on a 
sterilised slice of potato, where the curled and folded structure of the 
colonies is quite distinet, in consequence of the large dimensions they 
attain. The colour changes thereby into flesh-red. Old cultures grow 
soft in consequence of a dissolving process the slimy substance. 
The compounds which can provide the carbon and nitrogen 
nutrition of this species were determined by means of the auxano- 
graphic method ®, this giving in a simple way a measure for the 
difference in assimilability of the nutritive substances. 
With KNO, as source of nitrogen, a feeble growth was observed 
with glucose and maltose. Kalium-succinate, malate, malonate, citrate 
and caleium-tartrate, gave rise to a vigorous growth. No growth 
was obtained with cane sugur, milk sugar, mannite, galactose and 
oxalic acid. | 
The auxanograms prove that tartrate belongs to the best assimil- 
able substances, which explains why its use in the accumulation 
experiment with canal water produces such good results. 
With kalium-citrate as source of carbon, NH, Cl, KNO, KNO,, 
asparagin, kalium-asparaginate and pepton, could serve as source of 
nitrogen. 
B. stutzeri: produces no invertin, does not split indican and ureum 
but it secretes diastase, although in very slight quantity. This latter 
fact explains the possibility of denitrifying by this species in solutions 
containing, besides the salts, only amylum and KNO,. In broth no 
indol and no sulphureted hydrogen are produced. 
B. stutzeri produces much alkali; even the presence of glucose 
does not prevent the production of it in a plate of broth gelatin. 
Very remarkable is the behaviour of B. stutzert towards free oxygen. 
If the arrangement of the moving individuals under the influence 
of the oxygen of the air*) is examined in the glassroom, we find an 
accumulation in a line at rather great distance from the meniscus. 
On the other hand, growth is only observed *) in the meniscus itself. 
Hence, in this respect the bacterium behaves quite in accordance with 
the aerobic spirilla. 
B. stutzeri is a very active denitrifying species; to broth could be 
added up to 4°/, KNO,, and up to 1°/, KNO,, without thereby preven- 
ting the development of gas. If in the before described way a “tube 
1) Beyerincx. L'auxanographie ou la méthode de I’hydrodiffusion dans la géla- 
tine appliquée aux recherches microbiologiques. Arch. Neerl. 1889, T. 23 p. 367. 
2) ENGELMANN, Zur Biologie der Schizomyceten. Botanische Zeitung 1882, Bd. 40, S. 320. 
3) Beijerinck, Ueber Atmungsfiguren beweglicher Bakteriën. Centr.bl. f. Bakt. 
1893, Bd. 14, S. 827. 
11 
Proceedings Royal Acad. Amsterdam. Vol. V. 
