of the Genus Hillhousia . 89 
that organism, except that the large globules consist of a salt of calcium, 
viz. calcium carbonate. 
An organism has also been described and figured by Virieux 1 under 
the name of Achromatium oxaliferum. He states that ‘ Schewiakoff y 
decrit un corps central a mailles plus larges que dans la couche peripherique : 
pas plus que West, je n’ai pu faire cette distinction ’. He does not find that 
the large globules in the spaces of the reticulum are of calcium oxalate. 
He expresses doubt as to the composition of the refringent granules in the 
threads of the reticulum, but is inclined to think that 4 ils sont tres probable- 
ment constitues par du soufre \ 
There is not the least doubt that the organism described by Virieux is 
Hillhousia mirabilis , and not Achromatium oxaliferum . His Fig. 1 shows 
the refringent granules of sulphur in the threads of the reticulum as seen 
after the removal of the large globules of calcium carbonate (consult 
Fig. % on PI. IX). His Fig. 3 shows the minute granules in the threads of 
the reticulum after removal of both sulphur and calcium carbonate. 
It appears, therefore, that neither Massart’s nor Virieux’s observations 
relate to Achromatium. That organism has several features in common 
with Hillhousia , the chief of which are the large inclusions of a salt of 
calcium and the smaller reddish grains in the threads of the reticulum. In 
Achromatium , however, the globules are asserted to be calcium oxalate and 
the reddish grains of the nature of chromatin. In Hillhousia the globules 
are certainly calcium carbonate (and not calcium oxalate), and the reddish 
grains consist of sulphur, similar to the sulphur grains in other sulphur 
Bacteria. The most profound difference is to be observed in the structure 
of the protoplast, which in Hillhousia consists of a uniform reticulum, 
whereas in Achromatium there is a differentiated peripheral zone with 
a much smaller reticulum. 
A copy of one of Schewiakoff s figures of Achromatium is given 
(Fig. 15) for comparison with Hillhousia mirabilis . 
Summary. 
The following is a summary of the genus and its two known species : 
Hillhousia , West and Griffiths, 1909. A genus of Bacteria of relatively 
large size, with shortly cylindrical cells from two to three times as long 
as their diameter, extremities hemispherical. Protoplast consisting of 
a slender network with meshes of fairly regular size. Within each mesh is 
included a large amorphous globule of calcium carbonate, and numerous 
smaller grains of sulphur are located in the threads of the network in such 
a manner that they occupy the interstices between the globules of calcium 
carbonate. There is no differentiation of any nuclear body from the 
1 Virieux, J„ : Sur 1 ’ Achromatium oxaliferum , Schewiakoff. Comptes Rendus, t. cliv, 1912. 
