From one of these dots a tube was inoculated and from this several plate cultivations were made. The colonies which developed on these plates were of two kinds, the majority being round, yellowish and of small size, a smaller number spreading out on the surface of the gelatin and slightly iridescent. These surface expansion colonies when examined with a low power appear like a milky drop, with very fine granular contents, the whole surrounded by wavy lines which follow exactly the irregular contour of the expansion. The small round colonies growing in the depth occur in the proportion of about 3 to 1 of the surface expansion colonies. The microscopic appearance of the bacteria composing the two kinds of colonies, is almost exactly similar, they are extremely small and regular in size, 0·75 µ × 0·5 µ to 0·7 µ × 1 µ. When spread upon a slide, they are not readily miscible with water, and appear greasy. Both colonies inoculated into glucose tubes produced acid. The existence of these two organisms was confirmed in the following way:--A glucose tube was inoculated from a drench in active fermentation; as soon as the liquid became cloudy, a second tube was inoculated from it by means of a platinum needle; from this tube the fermentation was carried through two more tubes; a plate cultivation was made from the last tube 10 hours after inoculation. Again, the two kinds of colonies developed exactly similar in every respect to those obtained from the streak cultures. It seems probable from these results, and also from a comparison of the fermentations made with the organisms from an actual drench,[176] and from purified cultures with those from a single organism, which are described in the present paper, that the action in the drenches is a symbiotic one in which two or more organisms take part. [176] J.S.C.I. 1892, 422. *The Fermentations.*--During the time occupied by the isolation of pure cultures of the bacteria, two fermentations were conducted with the supposed pure cultures. These fermentations (or rather the second of them, for the first was unfortunately lost through the breakage of a bottle) may prove of considerable interest as throwing some light on the symbiotic action of the two organisms. The first fermentation with pure cultures of the bacillus α (B. furfuris) obtained from a _single_ colony in glucose gelatin, was inoculated on September 16, 1894, the composition of the fermenting liquid being-- Glucose 27 grm. Peptone 1·4 " Salt solution 140 c.c. Water 860 " Pure calcium carbonate 10 grm.