696 ig REPORT—1899, 
actions are frequently poisons, and we all know of cases where such poisonous 
excreta of living cells act as stimuli to other living cells, if supplied to them in 
minimal doses and very gradually: I need only instance the effects of tobacco or 
alcohol on man, in illustration of this. 
Several observers have shown that in presence of a particular food-substance 
the living cell is stimulated to produce and excrete a particular enzyme, while the 
substitution of another food stimulates the organism to excrete a totally different 
enzyme. 
Now let us see if there is any evidence to support the hypothesis that some 
such stimulative action is exerted by one symbiont on another. To a certain 
extent we find such in the remarkable vigour and large size of the algal cells in a 
lichen as compared with the same cells living an independent life, and in the 
persistent zone of brilliant green and often hypertrophied cells of leaves in which 
certain fungi are living, the gigantic cells of the nodules on leguminous roots in 
which the bacteroids are living, and many other cases; but since it is impossible 
to say how far these are cases of merely enhanced nutrition, we will pass them by 
and seek for other instances. 
One of the earliest I can find is Hugo Schulz’s demonstration in 1888 that 
minute quantities of poisons such as corrosive sublimate, iodine, iodide of potas- 
sium, bromine, arsenious acid, chromic acid, sodium salicylate, or formic acid, 
when added to yeast in 10 per cent. grape-sugar solution, immediately raise the 
fermentative activity of the organism—as measured by the amount of carbon- 
dioxide evolved, Effront, in 1894, showed that hydrofluoric acid acts similarly on 
yeasts, butyric ferments, and mycoderma, and, later, that the same is true of 
formaldehyde, salicylic acid, picric acid, &e. 
What looks like another case in point is Johannsen’s results of experiments 
with seeds, buds, &c., treated with ether or chloroform: respiration is increased, 
and the whole course of metabolism so altered that in some cases buds of flowers 
can be stimulated to open long before their normal period. 
The results obtained by Farmer and Waller with carbon-dioxide, which was 
found to induce an initial acceleration of the movement of the protoplasm in 
Elodea, may be a further instance. 
Pfetler has recently called attention to a still more remarkable instance—that 
it is possible by etherising the living cells of Spirogyra to alter the type of nuclear 
division from mitotic (indirect) to a-mitotie (direct). Massart had shown that 
callus, the hypertrophied tissue developed under stimulation by mites, fungi, 
exposure to air, &c., is formed of cells which divide with @-mitotic nuclear division ; 
and other cases occur. But it is even more to the point for my purpose that 
Gerassimoff, in Pfeffer’s laboratory, found Spirogyra driven to a-mitotie division 
by associated bacteria and other organisms, which he regards as a case of 
symbiosis. 
Now it may be regarded as certain that if a cell can be thus stimulated to 
alter the details of so fundamental and complex a morphological process as its 
cell-division by the action of associated organisms, the metabolic activities of its 
protoplasm are being driven into very different channels from the normal, and 
many physiological processes must be affected. 
Of course I am here raising questions which concern the border-line between 
health and disease, and much investigation is still required as to the meaning of 
these matters; but I ought to add that according to Pfeffer the etherised cells can 
be again restored to their normal state if the traces of anesthetic are washed out, 
and those familiar with Kleb’s experiments on other alge will appreciate the 
significance of this one with Spirogyra. ( 
However feeble the evidence may be, we can at least say, then, that there is 
some evidence in support of the hypothesis that one symbiont may stimulate 
another by excreting some body which acts as an exciting drug to the latter—just 
as truly as certain drugs act as stimulants to some cell or organ of a higher 
animal, and no doubt in a fundamentally similar manner. It will be noted that 
such drugs are frequently excreta from vegetable cells. , 
But there is another, perhaps more indirect way in which one symbiont may 
