A New Genus of Thread -Bacteria. 
29 
1906-7.] 
the experiments which were unsuccessful, it will be sufficient to describe 
the only one out of many which was successful in cultivating Spirophyllum 
ferrugineum. A small portion was inoculated into a solution made up 
of sterilised well-water, to which freshly precipitated ferric hydroxide had 
been added, and contained in a sterilised flask. The culture was allowed 
to remain on a table exposed to sunlight. I think the exposure to the 
sunlight was the determining factor in deciding which form should be 
preponderant, for, being protected by the iron compound, the light was 
more harmful to the other forms. In two or three weeks a flocculent 
red deposit was obtained, in which I found that nearly all the ferric 
hydroxide which I had added had attached itself to the organisms, which 
accounted for the very flocculent nature of the deposit, as ferric hydroxide 
placed in water under the same conditions settles down at the bottom 
of the flask in the same way that fine sand would. The appearance of 
the organism differed in no way from that found in nature, consisting 
of the usual spirally twisted bands, coloured deep brown, and thickly 
covered in most cases with conidia. As the development took place 
during vacation time, I could not examine the various phases of growth 
from day to day. I hope to communicate these results in a later 
publication. 
The Iron Deposit. 
The interpretation of the deposition of iron in these bacteria has 
undergone many phases. Cohn (3), who was the first to observe these 
bacteria, compared the deposition in Grenothrix polyspora to the deposi- 
tion of silicon in diatoms, and calcium carbonate in certain cell membranes 
of the Melobesiacese. In 1878 Zopf (8) examined the same organism, 
and came to the conclusion that cell activity had nothing whatever to 
do with the deposit, and that the deposition was purely a mechanical one, 
the iron being caught by the mucilaginous layer which surrounds the 
cell. He maintained that the iron was retained in this mucilaginous layer 
in the same way that the colouring matter is retained by the gelatine in 
certain coloured jellies. In 1888 an article appeared by Winogradsky (7) 
in which a totally different explanation was given. He came to the con- 
clusion that the soluble bicarbonate FeH 2 (C0 3 ) 2 in the water was absorbed 
into the cell, and there oxidised, being changed into ferric hydroxide. The 
change can be represented by the equation 
2FeC0 3 \ + 3H 2 0 + O = Fe 2 (OH) 6 + 2C0 3 
H 2 C0 3 j =h 2 o + co 2 
This oxidation is the source of energy of the plant whereby the vital 
