very variable. Freudenreich found, in the Kefir grains examined by him, a Torula and three bacteria, among these the Bacillus caucasicus. The last appears to be always present with an alcoholic yeast fungus. Besides the two saccharomycetes mentioned, several other species of Saccharomyces are cited as being found in Kefir.

In Armenia a beverage called Mazun, similar to Kefir, is prepared from milk. According to Emmerling the exciter of fermentation consists of a white, fatty, cheese-like mass which can be preserved for a long time. After a short time it produces alcoholic fermentation in the milk; simultaneously the casein coagulates, acid being formed, and a smell of fatty acid ester is developed. In this mass Emmerling found the following micro-organisms: yeasts among which were a number of coloured species, Oidium lactis, some other mould fungi, a yellow Sarcina and the common hay bacillus (Bacillus subtilis), also some cocci and the Bacillus acidi lactici, Hueppe. The last-named and the cocci turn the milk sugar into lactic acid; the milk sugar is also hydrolysed and thus rendered susceptible to the attacks of the yeasts. This fermentation is thus also the result of a fortuitous co-existence of bacteria and yeasts. As already mentioned, Lindner found Sacch. anomalus in this beverage.

Finally, we shall describe another species of Saccharomyces which was found in the exudations from oak trees, namely,

Saccharomyces Ludwigii, Hansen (Figs. 77, 84 and 85). -This species is the transitional form to the next genus, as with it something between a typical budding and a simple division takes place. It is in many respects so remarkable that it deserves a somewhat closer description. It is probably the only Saccharomyces which can be immediately recognised by microscopic examination. Although the vegetative cells possess all possible shapes, the lemon shape is the most prominent; it reminds one somewhat of that

a symbiosis. This does not agree with the original signification of the word, since in the cases cited it is only a question of a casual co-existence, a mixed fermentation; otherwise every fermentation in which two or more species appeared would be a symbiotic fermentation. By symbiosis was formerly understood an intimate relation which is, physiologically, beneficial to both participants, and the lichens were given as an example of a real symbiosis. But there is nothing analogous in the above fermentations. There is really no longer a definable idea attached to the word symbiosis; it would therefore be best to cease using the word.

of Sacch. apiculatus, but the cells are far larger, and, besides, the appearance is quite different. The first stages of new growth are as in the preceding saccharomycetes: at a point on the cell a wart makes its appearance; but instead of a regular budding a septum appears by means of which the new cell will cut itself off. The genus Schizosaccharomyces has no budding whatever; but inside the cell this septum is formed. Thus Sacch. Ludwigii is in this respect related partly, and in fact most nearly, to the real saccharomycetes, and partly to the schizosaccharomy

FIG. 103.-Schizosaccharomyces Pombe, Lindner. Vegetative and spore bearing cells. a, Germinating spores.

6. (After Lindner.)

cetes on account of the septum formation. Under certain conditions it forms a typical mycelium, especially in old cultures (p. 199, Fig. 77).

Hansen's researches on spore germination (Figs. 84 and 85) have been already alluded to. In this respect the species is also distinguished from the other saccharomycetes and might well be classified as a separate genus. During germination a promycelium is formed and the yeast cells are developed from the latter. Coalescence of the young spores usually takes place in the early stages of germination.

This species forms spores very easily on gypsum blocks gelatine, and also in various nutrient liquids, e.g., in a per cent. saccharose solution. The spores are round, and 04 μ in diameter. According to Nielsen the cardinal ints of spore formation are the following:

At 34° no spores are formed.

32° to 324° C. the first indications are seen after 19 to 21 hours. 30° C.

18 to 19

Sacch. Ludwigii, according to Hansen, ferments dextrose and saccharose but not maltose. In dextrose-yeast-water it can produce up to 10 vol. per cent. of alcohol, but in beer wort only 12 vol. per cent. In a saccharose solution it sometimes dies off rather quickly, a behaviour contrary to that of most of the other Saccharomyces species.

2. Genus: Schizosaccharomyces, P. Lindner.

Vegetative increase takes place by fission and not by budding. This fission occurs through a septum being formed nearly in the middle of the cell; the septum splits and the cell divides into two cells often hanging together as if by a hinge.

Schizosaccharomyces Pombe, P. Lindner (Fig. 103), was found by Saare in Pombe (negro millet beer) from Africa. The two ends of the cells are often different; one is rounded, the other is encircled by a well-defined circular ridge which encloses the newly formed conical membrane. In exhausted culture solution the cells become shorter.

Spores are formed to the number of 1 to 4 in each ascus; they form more easily in culture liquids than on gypsum blocks. Germination takes place by means of a germinating tube. A film is not formed. The optimum temperature for the growth is 30° to 36° C. This species forms much alcohol, the large amount of which has no

deleterious influence on the growth. It is a form of t yeast, and ferments maltose, dextrose, saccharose and als dextrin; it contains invertin. This fungus is employed u advantage in South American distilleries, as it is able t stand the warm climate.

Schizosaccharomyces octosporus, Beijerinck (Figs. 8 104 and 105), was found by Beijerinck on currants from Greece, and by Schiönning on Italian raisins. Some of the cells are cylindrical, some oval, and in fresh wort culture they are 4-5 to 6 μ broad and 7 to 13 μ long.

a

FIG. 104.-Schizosaccharomyces octosporus, Beijerinck. A young growth in wort at 25° C. 1900. (After Schiönning.)

The remarkable ascus formation in this species (Fig. 86) observed by Schiönning is described on page 211. The number of spores is eight as a rule, but somewhat frequently only four are found; the number may also vary from two to seven. The shape of the ascus varies; so also does its size; the breadth is 6 to 10.5 μ, and length 14 to 20.5 μ The size of the spores is 3 to 5 μ. The latter are stained blue with a solution of iodine in potassium iodide (Lindner). They are formed copiously on solid nutrient substrata, more scantily on gypsum blocks and in wort cultures.

ording to Seiter they are formed on gypsum blocks at in six to seven hours. This species develops no film on rt, but at room temperature a weak yeast ring is formed a month.

It ferments maltose and dextrose, but not saccharose. chiönning states that this fungus forms in beer wort bout 14 per cent. Ball.) 46 vol. per cent. of alcohol in ree weeks.at 25° C., and 6.56 vol. per cent. of alcohol in ive months.

8

FIG. 105.-Schizosaccharomyces octosporus, Beijerinck. A young growth on wort gelatine; some cells contain spores. 1999. (After Schiönning.)

Schizosaccharomyces mellacei, Jörgensen, was isolated by Greg from Jamaica rum. The spores of this species are stained blue by iodine in potassium iodide (Holm). Altogether Greg is said to have found eight species of Schizosaccharomyces in the mashes in rum manufacture.

Order II.-Perisporacea.

The asci are enclosed in the so-called perithecium; the latter is an envelope more or less spherical, completely closed, and consisting of one or several layers of cells (Fig. 106 6).