404 GUSTAF FR. GOTHLIN 
ctenophores, I made some observations which convinced me that 
total inhibitions of the ciliary movement without any retraction 
of the rows may occur in specimens of Beroé under the influence 
of external irritation. Thus I found that closure of an electric 
current of sufficient strength in the longitudinal direction of a 
Beroé with the cathode at the sensory polar end of the animal 
is followed by a cessation of movement in all the swimming plates 
without the meridional rows being drawn in. For an inhibition 
of this sort, which affects the swimming apparatus directly with- 
out the agency of muscles, I use in this work the term “primary 
inhibition,’ in contradistinction to the secondary inhibition, previ- 
ously described by C. F. W. Krukenberg (’80, pp. 10-11), which 
is the result of the drawing in of the rows owing to contraction 
of the radial muscles. ; 
I also observed the occurrence of a primary inhibition due to 
mechanical irritation under the following circumstances. I had 
some specimens of Beroé living in glass aquaria and observed 
on several occasions that when an animal that was swimming 
along in a horizontal or almost horizontal direction collided with 
the wall of the aquarium the vibrations in its swimming plates 
stopped completely for some moments with all the signs of a 
primary inhibition. Subsequent inquiries in the literature showed 
me that the same observation had been made three years before 
by V. Bauer at Naples (710, pp. 235-236). 
The inhibitory effect just mentioned seemed to me not quite 
explicable if the ciliary movements of the animal were regulated 
- from the statolith apparatus exclusively in the way given above, 
as the mechanical effect of the impact of the animal on the wall 
of the aquarium would, of course, if it affected the balancers, be 
that the latter were caused to vibrate more violently than before, 
and consequently the number of ciliary waves per unit of time 
would be increased. It seemed to me rather (’17, pp. 17-18) 
that both the above statements as to inhibition indicate that the 
swimming plates in Beroé are influenced by inhibitory nerves. 
In order to examine this question more thoroughly, I returned 
to Kristineberg in the summer of 1919 and carried out there the 
experiments that are described in this paper. 
