1910-11.] New Genus of Iron-bacteria. 503 
ment. A comparison of the different stages showed that the conidium grew 
to a certain length, and then was pinched off from the mother-organism. 
In fig. 6 an individual is shown at this stage. Over the whole surface 
nodular projections are seen, which are conidia in process of formation. Of 
course one cannot see these with the same distinctness in a photograph as 
when looking through the microscope. On the same plate, a band of 
Spirophyllum is seen completely covered with conidia, all of the same size 
and shape; and though the individual outlines of the conidia cannot be 
shown on the plate, yet through the microscope there was no more difficulty 
in seeing them than in seeing the conidia of a mould such as Penicillium. 
Molisch’s remarks on the observations of other investigators on the mor- 
phology of the iron-bacteria are of a most remarkable nature. In effect it 
amounts to this, that any recorded phenomena which he cannot verify in 
his own cultures are to be put aside as being due to mistaken observations. 
Although he worked with pure test-tube cultures in his investigations of 
Leptothrix, whilst I worked from samples — almost pure cultures — taken 
from nature, it does not follow that all the morpho]ogical capabilities of 
an organism are always demonstrated in test-tube cultures. Every bacteri- 
ologist knows that such is very seldom, if ever, the case. Artificial cultures 
of an organism are notoriously different in character, both physiologically 
and morphologically, from cultures of the same organism growing free in 
nature. This applies particularly to the methods of reproduction ; and one 
is not surprised to learn that conidia-formation does not take place in test- 
tube cultures of Leptothrix. But to assume that because conidia-formation 
is not found in artificial cultures, therefore no conidia-formation can take 
place under any circumstances, in spite of the researches of other investi- 
gators — which is in effect the standpoint taken by Molisch — is to take up a 
very remarkable attitude. As Molisch denies the existence of conidia- 
formation in Leptothrix, which he has seen and investigated, so also the same 
incredulity is expressed with regard to my discovery of conidia-formation 
in Spirophyllum, which he has not seen. From this standpoint we could, 
with equal justification, assert that the morphological and physiological 
peculiarities of growth of any pathogenic bacillus inside the host cannot be 
true because the same phenomena had not been observed in test-tube 
cultures of the organism. I should like to state here, that the objections 
which Molisch has brought forward are objections as to facts, and not as 
to the interpretation of facts ; and such being the case, I can do no more 
than leave the matter in the hands of later researchers on this branch of 
bacteriology. The chief object of the paper is the publication of the 
photomicrographs which were taken at the time of the investigation, and 
