282 Proceedings of Royal Society of Edinburgh. [sess. 
On the other hand, the glucose peptone sea water medium which 
had been inoculated with a fragment of the fermenting weed,, 
heated to 80° C., developed acid, the amount of which was deter- 
ja- 
mmed by — baryta solution. 
10 c.c. after 3 days’ incubation at 37° C. required 2*2 c.c. — baryta 
= 0'01628 grms. propionic acid. 
10 c.c. after 7 days’ incubation at 37° C. required 2*68 c.c. of ~ 
baryta = 0*0198 grms. propionic acid. 
An experiment was then made on a larger scale with this 
culture fluid, which was sterilised and inoculated with some drops- 
of the liquid from a test-tube containing sea water, glucose, and 
peptone, and a fragment of the fermenting ulva. 
The flask containing the inoculated fluid was provided with a 
cork and an arrangement for collecting any gases which might be 
evolved, and was placed in an incubator, where it remained for two 
or three weeks, but no appreciable quantity of gas came oft'. The 
contents of the flask were then distilled with sulphuric acid, the 
distillate boiled with excess of barium carbonate, and the filtered 
solution evaporated to dryness. A small quantity of a gummy 
barium salt remained, which qualitatively resembled the crude- 
barium salt obtained from the fermentation of the weed, but its 
amount was not sufficient for any quantitative experiments. 
Attempts were next made to obtain colonies of the micro-organ- 
ism by employing a substratum of the weed itself. Some fronds of 
the ulva were pressed and dried, and then attached to glass plates- 
by weak gelatine solution. The plates so prepared were next 
sterilised by heat, and three of them treated as follows : — 
On No. 1, some sterilised gelatine solution was poured, previously 
inoculated with a droplet taken from a tube containing sea water 
and a fragment of ulva which had fermented but had not black- 
ened. On No. 2 some sterilised agar was poured which had been 
similarly inoculated ; and on No. 3 the same medium, inoculated 
from the same source, which had previously been heated to 80° C. 
for twenty minutes. 
Of these three plate cultivations, well-marked colonies appeared 
on Nos. 1 and 2. No. 3, was doubtful and too much dried up. 
