1906-7.] A New Genus of Thread-Bacteria. 33 
The most interesting feature of Spirophyllum ferrugineum, from a 
phylogenetic point of view, is that it serves as a bridge to connect the 
iron-bacteria Leptothrix, Gallionella, Cladothrix, and Crenothrix on the 
one hand, with the genus Spiromonas on the other hand, which is made 
a dependent on the thread-bacteria, and is not included in this order. 
Spirophyllum agrees with Spiromonas in possessing a flattened body 
thickened at the edge in the same way. The latter is also spirally 
twisted, though never showing more than one and a quarter turns, and 
is motile in the mature condition ; whilst Spirophyllum, as described above, 
may exhibit any number of turns, and is only slightly motile immediately 
subsequent to germination. Hence Spirophyllum can be placed midway 
between the other iron-bacteria and Spiromonas, and thus justifies not 
only the inclusion of Spirophyllum, but also of Spiromonas into the 
thread-bacteria. 
Summary of Characters of Spirophyllum ferrugineum. 
Body of cell elongated, flattened, and spirally twisted. The number of 
spiral turns may vary from a quarter turn to fifteen and more turns. The 
width varies from 1 jul to 6 /x. The length may reach to 200 /u. and possibly 
more. The middle portion of the cell has a thickness of jul, but the 
edge is thickened up to \ /jl. There is no definite membrane, but the edge 
is thickened so as to form a kind of rampart all round the cell. The ends 
are usually irregular, angular, and unsymmetricaL The spirals may be very 
close or very wide apart, but the majority of the individuals have spiral 
lengths three or four times greater than the width. The organism has, so 
far, been found only in iron- water, and, except in the youngest stages, is 
coated with a thick deposit of ferric hydroxide. 
Multiplication is effected by the budding off of conidia, the process 
being exactly the same as in Leptothrix ochracea and Gallionella ferruginea, 
viz., a budding off in large numbers. Each conidium has a single coat, is 
oval in structure, measuring about 1 ^ in width and 175 /u, in length. 
Each germinates by bursting open the spore membrane, the contents 
then being protruded, after which the young vegetative cell is freed 
from the spore membrane and for a short time exhibits a faint movement, 
partly of a trembling and partly of a pendulum nature. Conidia formation 
begins when very young, even before the twisting has begun, and may 
persist throughout the whole life of the individual, even when thickly 
encrusted with ferric hydroxide. Hitherto only one doubtful case of 
multiplication by vegetative division has been observed. Immediately 
VOL. xxvii. 3 
