640 Prof. W. M. Thornton. Opposite Electrification [June 17, 



In repeating the experiments the chief difficulties will be found to 

 be (1) in maintaining electrical contact between the wires and the drop 

 without excess of liquid ; (2) in the cells adhering to the slide and cover 

 slip ; (3) in distinguishing between forced movement of the cells and free 

 movement due to streaming. Whenever there is no movement either the 

 electrical circuit is broken or the cells are anchored. To avoid the dis- 

 turbing influence of ions from the poles tlie current should be reversed 

 every five to ten seconds of continued observation. 



The essential points are fresh cells, neutral liquid, high voltage and 

 resistance ; in addition to which the electrical conductivity of the liquid 

 should be less than that of the organisms. The reason for the latter is 

 that when it is greater the current avoids the cell, preferring to go by the 

 liquid. On the other hand, when the conductivity of the organism is greater 

 the current converges upon it. 



3. Infusoria. — From time to time attempts were made to obtain conditions 

 under which the effect could be demonstrated with certainty. Motility of 

 any kind gave trouble ; thus Faramcecium was found by Verworn* to move 

 to the negative pole ; but if the current is switched on while clusters of 

 the organisms are under observation, they will be found almost without 

 exception to burst towards the positive. This was also observed by 

 Verworn. Euglcna, again, bursts towards the positive. The cell contents 

 of Rotifers and of small fresh-water worms move towards the positive, the 

 sacs clearing on the negative side. Many similar observations were made, 

 but the results were, as a rule, not sufficiently marked or uniform for 

 repeated demonstration. These were all with cells in their natural habitat. 

 Dale,f by a careful examination of the movement of parasitic infusoria in 

 various solutions, arrived at the following results. The reaction of tlie 

 host — a frog — was always alkaline. In an alkalinated solution Opalina 

 ranarum moved to the positive (p. 310); Nyctotltcriis cordiforviis from a 

 freshly killed frog to the positive (p. 316); Balantidiutn entozoon, alkaline, 

 in strong currents to the positive, then later to the negative (p. 321); 

 BaUndidiiihi doiKftium. (p. 320), and Balnntidium duodnti (p. 332), first to 

 the positive and after some hours to tlu; negative. It is not stated whether 

 the organisms were then found to be living, l)ut is ol' interest to note that 

 the movement, whilst they were fresh, was in each case to tlie positive. 

 The reversal may be compared with that of ]>lants given in the next 

 section. In acid solutions the movements were in general reversed, but the 



* ' I'syflio-phyHiolof^iaclu! ProtiHtetistudion,' Jena, 1889, 



t II. II. I>;ilc, '.Toiiiii. of I'liyHiolofry; vol. 26, j)]). 21!) e< sey. 



