1921] MEIER—ROOT TIP . IIs 
experimented further with the effect of the current on unicellular 
organisms. Using platinum electrodes, he passed a direct current 
through a drop of water containing Actinosphaerium. The first 
visible effect of a weak current was the contraction of the pseudo- 
podia lying in the direction of the electrodes. If the current was 
continued or increased, the pseudopodia lying in the path of the 
current became vacuolated, the vacuoles on the periphery burst, 
and the protoplasm of the rounded central portion of the organism 
began to disintegrate on the side toward the anode. This con- 
tinued until the whole organism was disintegrated. KiHNE states 
that the phenomena described for Actinosphaerium hold in general 
for such forms. 
VERWORN (21) repeated and verified KijHNe’s observations, 
using non-polarizable electrodes and extending the work consider- 
ably, especially with reference to free-swimming protozoa. He 
found in Paramoecium and other free-swimming forms a shrinking 
at the end toward the anode and a swelling at the opposite end, 
which phenomenon he regards as illustrating a general tendency to 
increased contraction on the side toward the anode. He found that 
some protozoa migrate toward the anode, others toward the cathode. 
CARLGREN (3) observed that in Volvox the long axis of the colony 
is placed parallel to the lines of the current, and that there is a 
movement toward the cathode. If the current is long continued, 
the colonies move away from the cathode and sometimes gather at 
the anode. The movement of the flagella on the side toward the 
anode was inhibited, that on the opposite side not affected. Simi- 
larly to VERWORN’s observation on Paramoecium, CARLGREN 
noticed in Volvox an anodal shrinking and cathodal swelling with 
migration of the colony-forming cells (gonidia) within fixed colo- 
nies toward the.anode. It is interesting to note his further 
statement that strong currents produced shrinking and swelling on 
the sides toward the anode and cathode respectively in dead speci- 
mens. Furthermore, he produced this shrinking and swelling in 
dead Paramoecia and Amoebae. CARLGREN concludes that the 
physical effect of the current (electrophoresis) accounts for many 
of the supposed stimulation effects on free swimming forms, and 
that it plays a large part in electrotaxis. 
