420 GUSTAF FR. GOTHLIN 
During my stay at Kristineberg in 1919 no ctenophores were 
obtained except Beroé. I had thus no opportunity of directly 
comparing the automatism of the swimming plates of Beroé and 
of other ctenophores under similar conditions. But to judge 
from my recollection of my visit to the same place in 1913, 
when I had a fairly plentiful supply of Bolina and Pleurobrachia, 
the automatism in mechanically isolated swimming plates is, at 
least in Bolina, considerably greater than in Beroé. 
My experience shows that a large amount of material of Beroé 
is needed in order to find in the shaken preparations any isolated 
swimming plates that continue to vibrate sufficiently long to 
make it possible to test the effect of an electric current on their 
automatism and frequency. I was only able to achieve this 
desideratum in two experiments, one of which will shortly be 
described. Before doing so, however, I shall give a short account 
of my arrangements for studying the influence of the current on 
isolated swimming plates. 
The material that had been obtained by shaking was trans- 
ferred to and observed in a glass chamber constructed as follows. 
On a microscope slide a strip of wax is poured, 3 mm. high and . 
3 mm. wide, in the shape of a rectangle, so that it encloses a 
basin 37 mm. long by 18 mm. broad. At the middle of each short 
side a:strip of wax 9 mm. long was removed and in its place there 
was fixed by means of Canada balsam, a strip of rattan of the 
same dimensions, the pores of which were directed from the outer 
side to the inside of the strip. Before each experiment the basin 
stood overnight filled with sea-water, so that all the pores were 
filled with this. 
The microscope slide with the chamber is placed on the stage 
of a microscope. The clay points of two Du Bois-Reymond 
“Thon-Stiefel-electrodes’ are placed one at the outer side of each 
rattan strip. The source of the current is the same as in previ- 
ous experiments. A commutator allows one to make whichever 
electrode is desired the cathode. 
Experiment 3/8.’ The basin is filled to a height of approxi- 
mately 2 mm. with the shaken preparation made from a Beroé 
that previously had a rapid ciliary motion. At about 6 mm. 
