548 



Prof. A. B. Macallum. Acineta tuberosa : [Feb. 19, 



6. The condensation of potassium in the superficial layer of the extended 

 tentacles, and the diffusion downwards into the cytoplasm when the tentacles 

 are being retracted, indicates that the Gibbs-Thomson principle of con- 

 densation, due to the action of surface tension, is the factor in bringing 

 about the concentration of potassium salts in the superficial layer or film 

 of each tentacle, and that the deposit on the cytoplasm-germ interface, as 

 well as those on the cytoplasm-spherule interface, would appear to be due to 

 the operation of the same principle. 



7. Surface tension thus makes the concentration of potassium in the 

 cytoplasm of the cell body of Acineta less than 1 in 275,000, and condenses 

 it to an extraordinary degree in the surface film of each tentacle, and at 

 other interfaces where the tension is low. Surface tension is, therefore, 

 an all important factor in determining the distribution of potassium salts 

 and, inferentially, of other solutes in active Acinetce. 



8. How the low surface tension is brought about which leads to the 

 formation of the tentacles is not known. With microchemical methods for 

 demonstrating fat, very minute spherules of fat are found in the superficial 

 layer or film of each tentacle, and the superficial film of the capitate end 

 of a tentacle may be, now and again, deeply impregnated with fat. Fat 

 or lipoid substance may, consequently, be the cause of the low tension. It 

 is, however, suggested that amino-acids are the substances which lower the 

 surface tension. 



9. The quantity of potassium salt condensed in the surface film of each 

 tentacle appears to be of greater concentration than obtains in the sea water 

 of the habitat of the organism. This inequality of concentration on the two 

 sides of the surface-film-seawater interface is, it is explained, due to the action 

 of surface tension in maintaining: the condensation on that side of the interface 

 where the surface tension is less. Lipoids, it would appear, are not concerned 

 in preventing the exchange of potassium salts, for they should also prevent 

 the penetration of the surface film by potassium salts derived from the 

 underlying cytoplasm. 



10. The current conceptions regarding cellular osmosis and the distribution 

 of salts in living cells, based on the van 't Hoff- Arrhenius theories of solutions, 

 must be revised. 



VI. LITERATURE. 



1. Benson, C. C, ' The Composition of the Surface Layers of Aqueous Aniyl Alcohol," 



'Anier. Journ. Phys. Chem.,' 1903, vol. 7, p. 532. 



2. Czapek, Fr., " Ueber die Oberfiachenspannung und den Lipoidgehalt der Plasniahaut 



in lebenden Pflanzenzellen," 'Ber. d. d. bot. Gesellsch.,' 1910, Jahr. 28, p. 480. 



3. Forch, C, " Die Oberfiachenspannung von anorganischen Salzlosungen," ' Ann. der 



Physik,' 1905, vol. 17, p. 744. 



