Cholnoky: Cell Structure and Environment 367 



System of Kolkwitz. This was, however, not based upon precise observations 

 or experiments but on an untenable hypothesis (Kolkwitz and Marsson, 1902, 

 1908, 1909; Kolkwitz, 1950; Liebmann, 1951, etc.). As a basis for the hy- 

 pothesis it was assumed that the substances (of which no one then bothered to 

 ascertain the chemical nature) which were responsible for the pollution of 

 waters could be removed first by reduction and subsec^uently by oxidation. 

 The so-called reduction phase was called polysaprobic and the oxidation phase 

 mesosaprobic. Naumann (1932), however, had shown that this hypothesis 

 was untenable: he demonstrated the nonexistence of a reduction phase and 

 consequently it was found impossible to judge the quality of waters, let alone 

 to purify them, on Kolkwitz principles. Under these circumstances it was not 

 surprising that cytologists found no reason to study protoplasmatic changes 

 attributable to "pollution" according to Saprobic System concepts. 



It was only much later that greater stimulus was given by the ecological 

 work of Kolbe (1927, 1932), who showed that certain diatom species are better 

 adapted to a high salt concentration than others. In his opinion it was the 

 chloride ion of sodium chloride which was responsible for the phenomenon of 

 adaptation. He also attempted to prove that in the absence of the afore- 

 mentioned ions (oligohalobic conditions), a moderate concentration (meso- 

 halobic conditions), or a high concentration (polyhalobic conditions) simulating 

 salt water was responsible for the distribution and adaptation of certain 

 species. 



Almost at the same time it had been shown (Cholnoky, 1929) that the diatom 

 associations of the soda lakes of Hungary (which contain carbonates and not 

 chlorides) were identical with those of Kolbe's mesohalobic waters of Speren- 

 berg. From these observations it was possible to deduce the fact that pri- 

 marily it was not the chemical composition of the salt molecules but rather 

 their concentration which was responsible for the halobic phenomena. In 

 other words, it was not the chloride ion at all, but the prevailing osmotic 

 pressure, i.e., molarity. It also became clear very soon after that the prevail- 

 ing osmotic pressure in the Hungarian soda lakes can be as high as, or even 

 higher than, that of the sea (a concentration of 2 mol. sodium carbonate is not 

 exceptional in the lakes), and that these high values do not necessarily give 

 rise to the growth of typical marine algae. It was recognized that it was not 

 the absolute salt content or molarity, but the variation of osmotic pressure 

 which produces the necessary conditions for the so-called brackish water 

 species; or put more precisely, the ability to withstand the molarity variations 

 gives advantages to these brackish water species. 



Because the variation of osmotic pressure mainly affects the protoplasm of 

 the brackish water organisms, it was clear that protoplasmic differences must 

 exist, and that these differences could only be discovered by studying the 

 living cells. 



After the classical studies of de Vries (1871, 1885), one could assume, as a 

 matter of course, that an increase in osmotic pressure would cause plasmolysis, 

 and also that plasmolysis could be neutralized by permeance to, or active uptake 

 of, the plasmolyzing substances. Hofler showed (1918, and more accurate 

 concept 1931) that de Vries's concept of semipermeability was untenable. 



