Cholnoky: Cell Structure and Environment 369 



repetition of ihis operation, the formation of the so-called inner cell wall is 

 explained: it arises from an increase in the osmotic pressure of the environment 

 during the gradual drying up of the waters in the summer (Cholnoky, 19286, 

 1954; Kamija, 1938; Kuster-Winkelmann, 1949). These phenomena are clear 

 proof that the otherwise generally fatal plasmolysis does not alter, or alters 

 only to a Hmited extent, the structure of the protoplasmic colloids in the brack- 

 ish water species which are adapted to variations in osmotic pressure. These 

 species not only survive the ordeal but actually build a cell wall during the 

 process — a procedure which would be hardly thinkable if the metabolism had 

 been upset. 



The repeated reductions in pressure due to variations of osmotic pressure do 

 not occur without having any side effects. With brackish water diatoms the 

 reductions in pressure are the triggers for sexual reproduction (Cholnoky, 

 19296), because the dilution caused by the culture medium always gives rise, 

 in the diatoms, to sexual propagation, i.e., auxospore formation. 



A sudden dilution causes plasmorhexis in brackish water species. This is 

 evidence for their having comparatively many free salt molecules in the water 

 mantles of the micelles of their colloids, which can cause an osmotic pressure 

 (Cholnoky 1928a). Such phenomena do not occur in brackish water species 

 if the dilution is carefully made. But with marine species, a dilution, no 

 matter how carefully made, causes plasmorhexis and death. This can be 

 accepted as proof that the salts causing isotonia, are indispensable to the proto- 

 plasmic colloids, and are structurally part of, and inseparable from, the micelles. 

 But further experiments will be necessary to be able to evaluate the position 

 fully. 



Without further experiments it will be equally impossible to explain the 

 mechanism of the phenomena which Lenk (1953) called Seasonal Variation of 

 Permeability. Variation of permeability without change of protoplasmic 

 structure is unthinkable. Consequently it can be assumed that submicro- 

 scopical protoplasmic structure is also subject to seasonal variation which can 

 only be due to adaptation to altered conditions of the habitat. 



As I have already suggested, the behavior of freshwater algae which have 

 been killed by the permeation of salt molecules, indicates that they undergo 

 coacervation and lethal coagulation due to the penetration of the molecules. 

 These protoplasmic changes are a kind of a poison effect and leads from a study 

 of adaptation to the important study of resistance (Biebl, 1937, 1952). It 

 would, however, be inappropriate here to discuss fully all of the hitherto known 

 cytological resistance phenomena. 



From the point of view of cytophysiology, a study of the poisonous effects of 

 salts and the resulting cytomorphological changes (which are often submicro- 

 scopical) is all the more important, as far reaching deductions regarding 

 adaptation phenomena will be possible. The studies on Melosira areiiaria 

 (Cholnoky, 1934) may be regarded as a beginning; and subsequent work on 

 cellular changes in other species and other algal groups (Ulothrix, Oedogonium, 

 Zygnemales, Desmidiales, and Siphonocladiales) led to important ecological 

 and cytological regularities being discovered. The notes, manuscripts, and 

 data, however, remained unpublished as they were lost at the end of the war. 



The poisonous effects of some salts {e.g., sodium carbonate) could only be 



