A New Genus of Thread-Bacteria. 
27 
1906-7.] 
formed when a thick deposit of iron is present, as I have seen them in all 
stages in Leptothrix making their way through this deposit in the course 
of their development. 
The Structure of Conidia. 
The conidium is oval in shape (fig. 26, a), measuring about 1 /ul in 
width and about 17 5 n in length. There is very little variation from this 
size, and the conidia are thus exactly the same in size as those of Leptothrix 
ochracea and Gallionella ferruginea . By careful staining with methylene- 
blue or fuchsin, the presence of the external membrane of the conidium 
is easily observable. The contents appear, when stained, as a homogeneous 
material, but of course, owing to the smallness of these bodies, further 
information is not possible. 
Germination of the Conidia. 
This part of the investigation is not complete, for the conidia do not, 
as a rule, germinate in the deposit of the bed of the stream, and, as they 
are formed in such huge numbers, it is only a comparatively small number 
that will be able to germinate at all. If the water, however, he collected 
before it comes to the surface, or, at any rate, immediately after coming 
out from the earth, it will be found that the sediment takes a comparatively 
long time to settle on account of the activity of the enclosed Spirophyllum. 
When examined as soon as possible after, collection, a few stages in 
germination were observed. Fig. 26, b , obviously represents the condition 
in which the conidium membrane has been split at the polar end and 
the young cell thrust out : it seems to assume its flattened condition 
at once. In fig. 3 a stage is seen in which the membrane has been 
thrust away. Even at this stage the characteristic want of symmetry 
is observable. When stained with methylene -blue, no appearance of 
a limiting membrane could be observed, nor any differentiation of cell 
contents. It forms before staining a grey, semi-transparent, angular, 
flattened portion of protoplasm. 
The Young Vegetative Cell. 
In freshly collected samples, when sedimentation takes place very 
slowly, we see numerous examples of young vegetative cells. Fig. 12 
shows a very young condition and is a typical example. It is about 
1’5 /m in width and about 10 jj. in length. It is flat, grey, semi-transparent, 
and, like older specimens, is unsymmetrical and somewhat angular. In 
this particular specimen one of the ends is slightly rounded off, but this 
