New Genus of Iron-bacteria. 
501 
1910-11.] 
that Molisch regards Spirophyllum as a Gallionella which has grown up 
in the Gallionella form, and which has subsequently developed into the 
form characteristic of Spirophyllum. 
III. During the whole time that the investigation lasted (about six 
months) no traces were observed of any transitions between Gallionella and 
Spirophyllum. 
IV. Gallionella has never been known to be motile ; but in the case of 
Spirophyllum, the young forms, for a short time after emergence from the 
conidium, possessed an independent movement. This motility was con- 
fined to young organisms, the stoppage being evidently expedited by the 
deposition of iron on the surface. The young organisms are quite colourless, 
but as they get older their colour gradually changes into a reddish-brown 
tint, which becomes deeper with age, until the tint characteristic of the 
sediment is observed on the individual organism. 
V. I may say that I am well acquainted with the life-history of 
Gallionella, which I found growing in several places near Glasgow, and 
have published the results of my investigations,* so that it cannot be 
reasonably stated that I am not acquainted with the organism with which 
Spirophyllum is supposed to be identical. In my observations of Gallionella 
I noticed certain forms which seem to me to form the basis of Molisch’s 
criticism. As is well known, part of the membranes of the iron-bacteria 
after a certain age become changed into a mucilaginous substance, which 
has a great influence in determining the amount of iron which will later 
be deposited on the organism. When, therefore, a Gallionella thread 
becomes so mucilaginous that the mucilage fills the spaces between the 
windings of the thread, an appearance somewhat similar to a Spirophyllum 
band is obtained. In such cases, however, as can be seen by reference to 
figs. 3, 4, 5, and 6, the two organisms are easily distinguished by their ends, 
which are essentially different. Spirophyllum has square-cut ends, which 
can be observed in all stages of growth, whilst as Gallionella forms con- 
volutions the ends are rounded. Whatever forms these organisms possess 
later, the appearance of the ends is always a distinguishing mark. 
Another approach to a similarity in form is presented by the behaviour 
of Spirophyllum in some of its later stages, viz., during decomposition, when 
there is a tendency, though only occasionally, for the thinner middle part 
of the band to be detached, leaving behind the thicker edge, so that a 
superficial resemblance to Gallionella is presented. (See fig. 3 ; also ex- 
planation on p. 504.) If I had not followed the phases of the life-history 
* Ellis, “ A Contribution to our knowledge of the Thread Bacteria (I.), 55 Centralllatt fur 
Bakteriologie , Bd. xix., 1907. 
