788 



continuity was found. The portions I, II and 111 were each obtained 

 with individuals from a different culture. 



The cause of the diffeient behaviour of the cultures is probably 

 to be found in the fact, that the nutrient solution for the cultures 

 had not the same composition when used. The plasma colloids 

 probably form compounds with acids and bases and adsorb all 

 kinds of ions. If the nutrient solution were not of the same com- 

 position, then the behaviour of the plasma colloids (and it was 

 probablj- these colloids that were aflected by the electrolyte solu- 

 tions) need not be constant. That the fluid from the cultures had 

 not always (he same composition was pretty certain. 



The treatment of the alga, before 

 it was used in the experiment (com- 

 pare p. 783) was such that only the 

 culture fluid was removed completely. 

 That the treatment removed sub- 

 stances from the organisms themsel- 

 ves, is not probable. But this must 

 have been the case, when the wash- 

 ing in distilled water lasted longer 

 than half an hour. In that case the 

 sensitiveness to electrolyte solutions 

 was greatly increased. 



Only the curve for potassium 

 sulphate is (piite complete '). The 

 course of this curve is, for the most 

 acid solutions i from 0.00015 n. H,S0J 

 onwards, quite different fi-om that 

 for the most alkaline solutions start- 

 ing (from 0,00100 n. KOH). In the 

 latter case we can understand the 

 course, if we suppose, that the effect 

 of the salt and of the OH'-ion is 

 more or less additive. For the beha- 

 viour of potassium sulphate in com- 

 pany of H--ions (acid) there is no 

 question of addition. If we follow the curve in the acid solutions, 

 starting from the ordinate-axis, we see that the curve at fust enters 

 higher into the acid region, i.e. that small quantities of salt brought 



'0 I t 3 y 

 coTic.K,50, 



6 H s 9 10 

 0,01 mol. 



Fig. 1, 



1) For the most acid solutions the critical concentration was determined according 

 to the content of acid. 



