346 Hoyt: CULTURES OF SPIROGYRA 
The beneficial effect of the action of alga filaments, in rendering 
originally toxic water less toxic to other filaments of the same or 
another form (see p. 341-2), has been noted already. While the 
evidence at hand suggests the probability that this effect may be 
due to an absorptive (or adsorptive) action on the part of the 
filaments,—Nageli (20), Deherain and Demoussy (8),—and that 
it may be therefore directly comparable with similar effects pro- 
duced by other solids with very large surface exposure, it must 
be nevertheless remembered that such an effect may be also 
partially or wholly due to chemical alterations of the originally 
toxic substances, as if brought about by enzymatic or other 
material emanating from the plant. No evidence is available 
for a decision in this matter. The effects produced upon Spirogyra 
in toxic water, by sediment from the stock culture of this plant (III, 
33) or from a Nitella culture (III, 32), together with the compara- 
tive growth of the alga in water from the two cultures just men- 
tioned (III, 36, 37), may suggest a possible excretion from Spiro- 
gyra of material more harmful to itself than to Nitella. It appears 
that the question of toxic and antitoxic excretions may enter into 
problems of algal growth just as it has come to play so important 
a part in the physiology of the bacteria and fungi and, recently, 
in that of the higher plants. 
III. Sats 
It has been frequently shown for both animals and plants that 
the toxicity of many solutions of single salts may be counteracted 
- by the presence of other salts in the same solution, without regard 
to the physiological effect of the latter salts when employed singly. 
Loew (15, 16, 17, 18) would restrict this conception of the 
antagonistic action of two ions to the single case of calcium and 
magnesium. Benecke (1) showed that the toxicity of other salts 
than those of magnesium is counteracted by calcium, but ascribed 
the antagonistic action to calcium only. Osterhout (21, 22, 23, 
24, 25) has, however, observed antagonism between fourteen 
different pairs of ions, including potassium, sodium, ammonium, 
calcium, magnesium, strontium, and barium. Loeb (13) reported 
that the toxic effect of a pure NaCl solution, on the eggs of Fundu- 
lus, was partly counteracted by each of a number of salts, including 
