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Proceedings of the Koyal Society of Edinburgh. [Sess. 
of this organism from start to finish, and if I had not the appearance of 
the square-cut ends to assure me, and likewise my knowledge of the 
life-history of Gallionella, I should also have regarded Spirophyllum, 
if presented for observation only at this stage, as belonging to 
Gallionella. 
VI. Another remarkable attitude taken by Molisch is the position of 
doubt which he takes up with regard to my discovery of conidia-formation 
in Spirophyllum and Gallionella, and likewise to the previous discovery of 
the same mode of reproduction discovered by others in the case of 
Leptothrix. He regards the conidia as foreign particles which have 
accidentally been deposited on the organisms from the surrounding water. 
His reason for this attitude lies in the fact that in his pure cultures of 
Leptothrix ockracea , upon the success of which I should like to take this 
opportunity of congratulating Professor Molisch, no signs of conidia-forma- 
tion were apparent. In the first place, so far as Leptothrix ochracea is con- 
cerned, conidia-formation has been described both by Migula * and myself. f 
In this organism, however, the retaining power of the mucilage surround- 
ing the cells is so great that the conidia sometimes germinate in situ, with 
the result that in some cases outgrowths radiating in all directions from 
the organism can be seen, so that the latter looks like a porcupine, except 
that the ends of the “ bristles ” are rounded instead of being pointed. It is 
very difficult to understand how the presence of these outgrowths is to be 
explained except by the germination of conidia, which have not been able 
to free themselves from the organism which gave rise to them. Surely the 
outgrowths cannot be ascribed to foreign particles which have adhered to 
the organism. Further, I have seen threads of Spirophyllum and also of 
Leptothrix so beset with these conidia that the outline of the organism 
itself could only be seen as a dim outline barely discernible through the 
mass of conidia. In such masses the conidia were distinctly visible, each 
as a sharply defined oval body : the uniformity in size, the definiteness of 
the outline, allowed no possibility of confusion with foreign particles. 
Again, these oval bodies could not possibly belong to other organisms, for 
there were very few, if any, other bacteria in the water, and in any case 
they were too large to belong to any of the lower bacteria, and there was 
no trace of any other organisms. In a case of this kind, the final proof is 
afforded by an observation of the development of the structures in question. 
I was able to accomplish this by observing individuals on which the number 
of conidia was small. In such cases some were sure to be seen in the first 
stages of development. Small nodules could be seen in process of develop- 
* Migula, System der Bakterien. 
t Ibid. 
