1913.] A Study on the Action of Surface Tension. 539 



of the organism is raised or not is a question on which there is no evidence, 

 direct or indirect. It is, nevertheless, tacitly assumed that in other organisms, 

 which exhibit at points on their surface extensions of the protoplasm in the 

 form of pseudopodia or flagella. the negative answer to this question is the 

 correct one. It may turn out eventually to be the right answer, but, on 

 a priori grounds, it is not improbable that in an organism like an Amoeba 

 the distribution of energy may be so adjusted that the tension over the 

 general surface may be raised. In a specimen of Amoeba which has been 

 moving continuously in one direction for more than four or five times its 

 diameter such an elevation of the tension must be continuously occurring, as 

 otherwise the film at the point where the pseudopodium develops would 

 spread over the whole surface and movement would quickly cease. 



However much uncertainty there is on this point there is none on the 

 question of relatively low tension in the films of the tentacles. The surface 

 tension in these may be the same or lower than it was before they were 

 protruded, but when they develop the tension is in all cases less than 

 that of the general surface as otherwise there would be no development of 

 tentacles. 



There should, in consequence, be in the surface films of these tentacles the 

 condition which promotes surface condensation as the result of the action of 

 the Gibbs-Thomson principle. The solutes which lower the surface tension of 

 the tentacles should be found in greater concentrations in their surface films 

 than elsewhere in the cytoplasm of these organisms. 



This is the case with the potassium salts. When these organisms, in the 

 very active condition, are treated, after the manner described above, with the 

 hexanitrite reagent, followed by washing in ice-cold water and by application 

 of ammonium sulphide, the distribution of potassium salts thus revealed is, in 

 the vast majority of preparations, like that represented in fig. 3. In such the 

 potassium is seen to be localised in the surface films of the tentacles, at the 

 interface formed by the maternal and germinal cytoplasms and at the inter- 

 face formed by the cytoplasm and each of the included spherules. Elsewhere 

 in the cytoplasm the potassium salt is so minute in quantity as to be 

 undemonstrable by the reagent employed for that purpose. 



The occurrence of potassium salts at the interface formed by the maternal 

 and germinal cytoplasms is in part at least due to surface condensation. The 

 film covering the germinal cytoplasm must have a tension less than that of 

 the film of the adjacent maternal cytoplasm, as otherwise the germinal bud 

 would not develop in the central cavity of the organism. The condition at the 

 interface would then be more or less like that at the interface formed by a 

 drop of oil suspended in water, in which salts, e.g. those of potassium, are 



