Ward . — Thames Bacteria , III. 
199 
A more important point seems to be that no one has con- 
tradicted Hausers main facts, which are the following: — 
these three ‘ species ’ occur together in putrefying flesh- 
infusions, and form rodlets in long filaments : the rodlets 
are about 3-4 /x long and o -6 /x broad, or somewhat longer or 
shorter, P. Zenkeri being smaller and only about 0-4 /x broad. 
All motile : no spores known, but all endure drying up. 
The principal characteristics as given by Hauser are the 
remarkable yellowish-brown and grey plate-colonies which 
consist of radiating mycelium-like, tendril- and hair-like 
filaments thinning out from a central mass of twisted tresses 
which in all but P. Zenkeri form zoogloea-masses. On the 
surface of the gelatine these spread out as ‘ wandering islets ’ 
of closely serried rodlets arranged in the most remarkable 
helicoid, tendril-like and irregular figures, which continually 
change their shapes. The first two forms liquefy the gelatine, 
but P. Zenkeri does not. 
In stab-cultures the gelatine is liquefied rapidly by P. vul- 
garis , slowly by P. mirabilis , and not at all by P. Zenkeri. 
On agar, P. vulgaris rapidly spreads as a thin greyish layer, 
and on potato it forms a dirty slimy mass. Hauser gives no 
particulars as to the behaviour of the other two on these 
media. All these forms do best at 20-24° C., and grow 
quickly. They are also facultative anaerobian, and their 
products are toxic. 
Zimmermann 1 found P. vulgaris and P. mirabilis in the 
river, and confirms Hauser’s descriptions 2 , adding particulars 
as to their behaviour in broth and on potatoes. The broth 
becomes turbid, and greyish flocks are deposited. Lustig 3 
gives all three species, and quotes several observers as having 
found them in water. He also adds that P. Zenkeri does 
slowly and partially liquefy the gelatine after some time. 
1 1. c. pp. 66 and 68. 
2 Zimmermann says, however, that B. mirabilis does not liquefy 10 % gelatine, 
and does best at 24-30° C.: this suggests either great variability or that he did not 
keep his gelatine cultures long enough. 
3 1. c. pp. 89-91. 
