PRIMARY INHIBITION OF CILIARY MOVEMENT 437 
a statement of R. Hertwig to the following effect: ‘‘ Die Faden 
des Meridiannerven reichen so weit als die Flimmerrinnen; wo 
diese mit einer Verbreitung an dem ersten Ruderplittchen auf- 
héren, finden sie ebenfallsihr Ende . . . . Nur bei Beroé 
ovatus schien sich mir der Faserzug auch weiter iiber den bezeich- 
neten Punkt hinaus unter die Plattchenreihen zu verlingern.”’ 
There is undoubtedly an intimate connection between primary 
and secondary inhibition of the ciliary apparatusin Beroé. Ifinan 
intact animal one wishes to produce primary inhibition by touch- 
ing the edges of the mouth, or; still more, if one wishes to produce 
it from the polar fields, the mechanical stimulation must be car- 
ried out delicately. If the intensity of the stimulation is the 
least bit overdone, secondary inhibition occurs instead. In the 
case of the atropin-poisoned animal it was observed (experiments 
7 and 8) that certain electrical and mechanical stimulations, which 
in a normal animal produce primary inhibition, caused secondary 
inhibition instead. I imagine, therefore, that both the primary 
and the secondary inhibitory apparatuses make use of the same 
receptors, but that the inhibitory nerve endings at the neuroid 
conducting tissue in the row are caused to function from the net 
of nerves by impulses of weaker intensity or less extension than 
the nerve endings in the smooth muscular cells need to cause their 
effector organs to contract. 
As Verworn has shown, there occur in Beroé conditions when 
the animal systematically corrects a horizontal or slanting posi- 
tion to a vertical position’ and when the change in position is 
connected with primary inhibition or a-slowing, respectively, of 
the ciliary motion in certain topographically defined rows. 
With regard to the situation of these rows, when the animal cor- 
rects a horizontal position at the bottom, see experiment 11. 
A question connected with the present subject is whether the 
primary nervous inhibitory mechanism in Beroé is of any impor- 
tance for the regularity of these corrections of position.. In this 
question I have by my experiments arrived at the conclusion 
that in certain cases it is impossible to explain away the existence 
of an influence of this sort, but that it is of minor importance in 
comparison with the regulation caused by the statolith appara- 
