260 A. B. MACALLUM. 
ends, while others had an oval shape, but the majority were 
cylindrical with flat end-surfaces. Several cover-glass prepara- 
tions of the organisms, fixed by heat and subsequently placed 
in alcohol, were made, but no cultivations were attempted, 
since before its value for the purpose of this investigation 
was ascertained, the original culture fluid had been thrown 
away. 
One of the cover preparations was subjected to the prolonged 
action of the glycerine and sulphide mixture, but, as sometimes 
happened in other cases, no result was obtained. The other 
two were placed in sulphuric acid alcohol for about eight hours 
at a temperature of about 25° C., and then treated in the usual 
way with the acid ferrocyanide mixture. One of the prepara- 
tions was also stained with eosin, and both were, after being 
washed in water, dehydrated with alcohol and mounted in 
balsam. Examples of the organism exhibiting the Prussian 
blue reaction and the eosin stain are represented in fig. 53. 
The eosin reveals a large central body, sometimes of irregular 
shape, and always lying free in a cavity in the markedly reticular 
cytoplasm. The body in question contains no iron, but in other 
respects resembles the large body present in Saccharomyces 
Ludwigii. Theiron demonstrated appears to be ina granular 
form distributed in the trabeculz of the cytoplasm, though 
sometimes a very large granule, richly supplied with iron, was 
found adjacent to, or in contact with, the large central body 
destitute of iron. 
As inorganic iron is a constituent of the sheath and other 
parts in species of Crenothrix and allied forms (C. Kiihni- 
ana, Leptothrix ochracea and Cladothrix dichotoma), 
it is possible that all of the iron observed in the form described, 
and whose relationship to Crenothrix has been suggested, 
was not derived from a ‘‘ masked” compound. The amount 
of inorganic iron must, however, have been very little, for, in 
the cover preparations subjected to the prolonged action of 
the glycerine and sulphide mixture, but a few of the forms 
gave an immediate reaction for iron. The chief difficulty lies 
in the fact that through the failure of the last-mentioned 
