284 Proceedings of Royal Society of Edinburgh. [sess. 
tubes were strongly blackened, but those in the fresh water tubes 
remained unaffected, except the one in the tube containing the 
unwashed weed. In 168 hours the unwashed weed in sea water 
was itself beginning to blacken, but the contents of the tap water 
tubes had still only faintly blackened their lead papers. Even 
after a month, the difference in the appearance of the contents of 
the two set of tubes was very noticeable. 
Zelinsky * has described an organism which he named Bacterium 
hydrosulfureum yonticum , and obtained from the ooze of the Black 
Sea, which reduces sulphates to sulphides, and evolves sulphuretted 
hydrogen. He employed a special culture fluid for its growth, con- 
taining 1 per cent, solution of ammonium tartrate, 1 to 2 per cent, 
solution of grape sugar, \ to J per cent, of sodium hyposulphite, 
OT per cent, of potassium phosphate, and traces of calcium chloride. 
We prepared some of this fluid and inoculated (sterilised) tubes 
of it with minute fragments of the following : — 
1. Ulva which had fermented with sea water for 12 months in 
a stoppered bottle. 
2. Ulva which had been fermented with tap water for the same 
time and under similar conditions. 
Lead papers were suspended in the upper part of each tube by 
cotton-wool plugs, and the tubes then placed in the incubator. 
We also prepared a similar set of tubes containing J per cent, of 
ferrous sulphate instead of the hyposulphite, and inoculated them 
in the same way. The first series we shall call A and the second B. 
In 99 hours the Lead papers in all the tubes were blackened 
except B 2, and a filmy growth was beginning to form on the 
surface of the liquid in two of the tubes. After a further interval 
of 24 hours, A 1 was covered with a pink growth, and A 2 with a 
white growth. A 1 was plated out in ordinary agar medium, but 
it gave no colonies, but A 2, similarly treated, gave plenty of well- 
defined colonies. Three of the latter were again plated out and 
inoculation from the resulting colonies made in tubes containing 
sterilised ulva and sea water, when after 5 days a whitish growth 
began to appear in the tubes, and 2 days later their contents were 
giving off sulphuretted hydrogen. 
* Zelinsky, Proceedings of the Russian Physical and Chemical Society , 
25, fasc. 5 [1893], 
