1913.] A Study on the Action oj Surface Tension. 



543 



low as that of the solution in contact with the oil droplets in Lewis' 

 determinations, and the concentration in the cytoplasm were M/20, then the 

 concentration in the condensation would be (5 x 10~ 8 x 100)-?-(6'7S x 10 -8 ), 

 or 73'7 per cent, of potassium ; 73"7 per cent, of potassium is equivalent to 

 1404 per cent. KC1, which is an impossibility. With a solution concentra- 

 tion less than M/20, on the other hand, the concentration of the condensation 

 in the surface films would still be high, probably higher than if it 

 corresponded to the value of the Gibbs equation for M/20, that is, 

 (1-7 x 10" 9 x 100)-r-(6-78 x 10" 8 ), or 2-5 per cent, of potassium, which is 

 equivalent to 476 per cent. KC1, or 0'638 M. 



If the surface film were constituted of molecules of protein in which 

 water was absorbed, the thickness of the zone would be very much greater 

 than if it were formed of water alone, and this would provide for a 

 concentration of potassium chloride much less than the impossible 140 - 4 per 

 cent., yet greater, perhaps very much greater, than the lower limit, 4 - 76 per 

 cent. 



With such a concentration in each superficial film, the precipitate would 

 be marked, but this would not be confined to the surface film, for the crystals 

 formed would project into the underlying zone. This, perhaps, explains why 

 the deposit seen under the high powers appears to have such a thickness as 

 indicated in fig. 6. 



What is the source of the potassium found in these condensations ? 



The amount of potassium found in the sea water around the wharf of the 

 Biological Station at St. Andrews, as ascertained from analyses made by the 

 author, ranges from - 0272 per cent, to - 0353 per cent, according to the tide. 

 As chloride the potassium of the higher concentration would correspond to 

 - 0673 per cent, or slightly less than M/110. The presence of potassium 

 salts in sea water suggests that the potassium salt diffuses into the organism 

 from without, but the author found that when a mass of the filamentous 

 Algte to which a very large number of Acinetce were attached, was placed for 

 24 hours in a large quantity of filtered sea water the majority of the Acinetce 

 examined contained very little potassium, although the tentacles were 

 protruded. Further, in a few of the Acinetce in every preparation there was 

 little or no potassium present. It may also be noted that sea water with 

 a concentration of - 035 per cent, of potassium will not give with hexanitrite 

 reagent a precipitate of the potassium salt which will at all compare in 

 density with the precipitate of the same salt in the superficial films of the 

 tentacles, and it is consequently improbable that the much higher concen- 

 tration of potassium salt in the tentacles is derived by diffusion from the 

 sea water. 



vol. lxxxvi. — b. 2 s 



