554 
Ward. — Symbiosis. 
of two yeasts in many beers, explaining certain peculiar after- 
fermentations as due to the results of one yeast acting on the 
medium improved for it by the other (38 a). 
The Japanese have long been in the habit of brewing a 
peculiar fermented liquor known as rice-wine, or Sake (39). 
Rice grains are steamed, and when cool are infected with 
a mould fungus now known as Aspergillus Oryzae. When the 
rice is quite mouldy, at which time it emits a peculiar odour 
like that of pine-apples, the starch is found to be rapidly 
turning to sugar, under the action of a diastatic enzyme 
secreted by the Fungus. 
This decomposing rice is then placed in water and exposed 
to the action of a yeast, which rapidly ferments the sugar, and 
the alcoholic Sake results. 
So closely is the yeast associated with the Aspergillus , that, 
in practice, the alcoholic fermentation commences soon after 
the enzyme of the Aspergillus begins to hydrolyze the starch 
of the rice, and for some time a controversy existed as to 
whether the yeast was not really part of the life-history of the 
Aspergillus. Several observers have now shown, however, 
that we have here a striking case of symbiosis (40). 
On reviewing these examples, we shall find that very 
different degrees of association of the organisms are to be 
met with. 
At the one end of the series we find two organisms merely 
associated for a short time, e. g. Bacilli and worms, bees and 
Botrytis- spores, and, so far as we may speak of symbiosis 
at all in these cases, it is merely temporary or disjunctive. 
At the other end of the series we have a close permanent 
combination of the two organisms working in unison, e. g. the 
Lichens, and Winogradsky’s Clostridium with its protective 
mantle of aerobic Bacteria ; also the ginger-beer plant and 
kephir. 
But between these extremes it is possible to find all stages, 
the half-way house being met with in cases such as the Sake 
ferment, where the Aspergillus evidently prepares the way for 
the yeast . 
