32 
Proceedings of the Royal Society of Edinburgh. [Sess. 
out oxygen. This would explain the fact that their presence expedites the 
precipitation of the hydroxide. In my experiments I have found that the 
presence of sunlight does not act as a deterrent to the growth of these forms, 
and it is just possible that we have before us organisms which beneath their 
iron deposit possess a certain amount of colouring matter performing the 
same functions as chlorophyll. I am at present engaged on this problem. 
Whatever the reason of this enormous attraction for iron may be, it is very 
thorough, for an analysis of a sample in which the iron had been precipitated 
showed not a trace of this substance in the water. 
Phylogenetic Position of Spirophyllum ferrugineum. 
Migula, in his System der Bacterien (4), defines the Chlamydobacteriacese 
as follows : — “ Zellen cylindrisch zu Faden angeordnet, die von einer 
Scheide umgeben sind. Vermehrung verfolgt durch bewegliche oder unbe- 
wegliche Conidien, welche direkt aus den vegetativen Zellen hervorgehen 
und ohne eine Ruheperiode durchzumachen, zu neuen Faden auswachsen.” 
This new form agrees with this definition in all essentials except that the 
body is flattened instead of being cylindrical, and is not externally limited 
by a membrane, which one would hardly expect in an organism of this 
shape. There is complete similarity in the methods of reproduction with 
the other iron-bacteria, all of which are included in the Chlamydo- 
bacteriaceae ; and in whichever family Leptothrix ochracea and Gallionella 
ferruginea are placed, that family must also take in this form, as they 
obviously form a natural group. Again, Gallionella ferruginea, renamed 
Ghlamydothrix ferruginea by Migula, possesses, according to this observer, 
only an extremely fine membrane, which, however, I have not been able to 
see, and Adler records the same failure; and in another, Ghlamydothrix 
hyalina, the membrane is altogether wanting. Again, Phragmidiotlirix is 
placed by Migula as a genus of the order Chlamydobacteriacese. This is 
described as consisting of cylindrical cells which later become flattened and 
disc-shaped. Hence the fact that, in the absence of a limiting membrane 
and in the presence of the flattened condition, we have characters not 
usually found in this order, does not exclude this new form from that order, 
in view of the obvious relationship to the other iron-bacteria, and in view 
of the non-universality of the excluding characteristics. I would therefore 
suggest that Migula s definition of the order Chlamydobacteriacese be 
altered to read thus : — “ Cylindrische oder flache Zellen, die gewohnlich von 
einer Scheide umgeben sind,” instead of “ Zellen cylindrisch zu Faden 
angeordnet, die von einer Scheide umgeben sind.” 
