274 Cc. U. ARIENS KAPPERS 
with a surplus of positive ions, will on the transmission of the 
constant current pass to the kathode. 
If we accept this theory as correct, we shall have to assume 
that in ordinary circumstances—under which the kathodie tro- 
pism or taxis predominates—also a greater charge of positive 
ions is present in the cell-body of the ameba, or in the proto- 
plasm of the tentacles or root-tips, than in the surrounding 
extra-protoplasmatic medium. This explanation is not gener- 
ally accepted, but that the condition of the extre-protoplasmic 
medium is of great importance has also been emphasized by 
Loeb and Budgett, who are equally inclined to ascribe the 
exceptions to Pfliiger’s law (the anodic migrations) to altera- 
tions in the extra-protoplasmic medium. They refer to a 
phenomenon which may be exhibited by that side of an ameba 
or paramecium that is turned to the anode, viz., the extension 
of the protoplasm on that side, eventually followed by lique- 
faction. This ancdic extension, first observed by Verworn 
(loc. cit.), is the first thing that appears when Protozoa are 
exposed to the constant current and precedes the real kathodic 
galvano-tropism. 
Loeb and Budgett (loc. cit.) have submitted it to a more 
detailed examination and also came to the conclusion that this 
process is a result of the extra-protoplasmatic medium. Their 
explanation of this anodic phenomenon differs from the one given 
by Coehn and Barratt. They are, however, equally inclined to 
consider this phenomenon as due primarily to changes in the 
extra-protoplasmatic medium2? in contrast to the phenomena 
of common tropism following Pfliiger’s laws of irritation. It 
may be mentioned still that the most favorable strength of cur- 
rent in those experiments with ameba was only 0.4 milliampere. 
Besides these galvano-tactic and galvano-tropic phenomena of 
living protoplasm, we know of polar phenomena in dead organic 
substances rendered evident by the direction in which albumen 
shifts when subjected to a constant current: viz., the phenome- 
27 Perhaps this mode of explanation may be also applicable to the above- 
mentioned reversal of the galvano-tropism of root tips and to the anodal phenom- 
enon observed by Bancroft (vide supra). 
