The Lime-Sulphur Bacteria of the Genus Hillhousia. 
BY 
G. S. WEST, M.A., D.Sc, F.L.S. 
AND 
B. M. GRIFFITHS, M.Sc. 
With Plate X. 
I N 1909 the authors published a preliminary account 1 of a new organism 
which they named Hillhousia mirabilis , and which they regarded as 
a giant sulphur bacterium. Since that date further investigations have 
shown that the organism is without doubt a huge sulphur bacterium, but 
one that contains in addition a large amount of calcium carbonate. 
Each individual organism is cylindrical with hemispherical extremities, 
and contains such a large amount of mineral matter that it has a specific 
gravity about equal to that of the small sand grains frequently associated 
with it. 
It is a peritrichous bacterium with relatively short cilia, and it exhibits 
slow rolling movements of a rather irregular and often of a spasmodic 
character. 
The cell-wall is very resistant to the passage of reagents, and has been 
shown to be lamellose. 
The organisms are gregarious but not colonial. They have a tendency 
to adhere to the bottom of a glass vessel, probably by means of the small 
amount of mucus secreted by each individual. 
They occur in the mud of freshwater pools, sometimes in very large 
numbers. Owing to their high specific gravity they can be obtained par- 
tially pure by gradually pipetting off the flocculent organic matter, when the 
organisms, mixed with a few small sand grains, remain. If the glass dish is 
carefully tilted the sand grains can be made to roll down, leaving the 
organisms as a greyish-white mass. 
Although it is thus possible to obtain a pure ‘ collection ’ all attempts 
at pure cultures have failed. Such cultures would necessarily be of slow 
1 G. S. West and B. M. Griffiths : Hillhousia mirabilis , a Giant Sulphur Bacterium. Proc. 
Roy. Soc., B, vol. lxxxi, 1909. 
[Annals of Botany, Vol. XXVII. No. CV. January, 1913 ] 
