A New Genus of Thread-Bacteria. 
23 
1906-7.] 
in which the twist-length is roughly four times the width. In exceptional 
cases, as in figs. 5, 6, a twist-length may be nine to twelve times longer 
than the width, and it may be said that nineteen out of twenty of the 
organisms have twist-lengths three or four times greater than the width. 
A noticeable feature of the twist is that it may be towards the right or 
towards the left, and it may exhibit both kinds, even in the same individual. 
The internal structure can be followed only in those organisms in which 
no deposit has yet taken place, or else in which it is so slight as not 
to interfere with the staining. There is no indication of a definite cell- 
wall such as is found, for instance, in Leptothrix ochracea. In place 
of it we find that the organism is thicker at the edges than at the 
middle, and there does not seem to be a sharp line of demarcation separating 
the two parts, though, owing to its greater thickness, the thickened edge 
is easily distinguishable when stained with methylene-blue or any other 
dye (fig. 11). 
By examination of stained specimens, and by carefully examining 
the edges at the parts where they are turned up, it is seen that a trans- 
verse section would appear somewhat like fig. 7. This is different to any- 
thing known among Bacteria, and is found only in the genus Spiromonas, 
which was found by Warming on the coasts of Denmark, and which is 
described as having a similarly thickened edge. Now, as Spiromonas 
Cohnu, which is the only known representative of the genus, is also a 
flat leaf -like organism, which curls in the same way, it would appear that 
this development has become necessary to subserve the purposes of twisting 
without danger of tearing. In the case of Spirophyllum ferrwgineum 
there is the additional necessity of strength imposed upon it, because each 
individual has to bear the weight of a large quantity of ferric hydroxide. 
In one case the edge of an organism had become torn away from the 
middle portion, showing quite clearly its nature, and bearing out what has 
been stated above on this point. 
The extremities of the individuals are very different from anything 
yet known in this division of the vegetable kingdom. Where the organism 
has made only half a turn, the extremities appear much narrower than 
the remaining portions, but this is due to the fact that at this point the 
organism is somewhat turned up (fig. 18). Where the end is flattened out, 
as in figs. 5, 10, 20, it is seen that the ends are as wide as the rest of the 
organism. The remarkable feature, however, is the fact that the ends 
are not neatly rounded off as we see, for example, in bacilli, but are 
unsymmetrical and angular. Examples are well shown in figs. 5, 9, 18, 27. 
When individuals are examined in which no deposition of iron has taken 
