PRIMARY INHIBITION OF CILIARY MOVEMENT 439 
a ciliary movement and is developed phylogenetically from a 
movement of this sort is under the influence of inhibitory nerves. 
These cilio-inhibitory nerves are at present only established by 
the manifestations of their function. With regard to their mor- 
phology, there is still very much to be decided; this is especially 
the case concerning the way in which they are connected with 
the meridional rows. ‘The second main result is that impulses 
which cause inhibition in distant organs are met with already in 
animals that lack a central nervous system. 
SUMMARY 
1. It is shown that in Beroé cucumis there occur conditions 
when all the swimming plates are inhibited in their movements, 
beat more slowly, or remain stationary in a position of rest, 
without any muscular retraction of the meridian rows. 
2. These conditions of primary inhibition can be produced by 
mechanical as well as chemical and electrical stimuli. 
3. Especially the primary inhibition which the author has 
found to occur when a galvanic current of about 2 milliamperes 
in density per cm.? is made to pass in the longitudinal direction 
of the animal with the cathode outside the sensory pole is acces- 
sible to an experimental examination in different conditions of 
the animal. The inhibitory effect of such a current issues from 
the cathode. 
4. Certain nerve poisons, namely, chloral hydrate (0.2 per 
cent) and atropin (>0.3 per cent), abolish the primary inhibi- 
tory effect of a current of the kind just mentioned. In animals 
treated with these poisons the closure of such a current produces 
at a certain stage, instead of inhibition, an acceleration of the 
ciliary motion. It is noteworthy that an acceleration is the nor- 
mal effect of closing a similar current in Bolina and Pleurobrachia. 
5. The primary inhibition of the ciliary movements in Beroé 
cannot be explained without the assumption of formations which, 
at least from a physiological point of view, serve as cilio-inhibitory 
nerves. ‘These are paralyzed by chloral hydrate and atropin, 
probably by cocaine as well. 
