438 GUSTAF FR. GOTHLIN 
tus. One way in which the inhibitory mechanism can contribute 
to the correction of position is as follows. When a Beroé keeps a 
horizontal position at the bottom it follows as a matter of course 
that a number of the swimming plates of the lower rows might 
be affected mechanically by their own vibrations, as they are in 
direct contact with the medium at the bottom—an immobiliza- 
tion of the plates on account of the weight of the animal can 
scarcely take place. It is conceivable that this mechanical 
stimulation has a local inhibitory effect on the ciliary motion in 
the corresponding rows, while the upper rows work without any 
inhibition, and that as a result of this the animal rises up. 
I have, as a matter of fact, seen two Beroés, a few days after 
the removal of their statolith organs by operation (experiments 
5 and 12), rise into a vertical position at the bottom of the aqua- 
rium, although the animals were quite unable to maintain this 
position afterward. If a vertical position is to be definitely 
taken up, the statolith organ is indispensable, but a temporary 
quasi-correction of a horizontal position is thus shown to be 
possible, by the cases referred to above. 
There are scarcely any starting-points for an experimental 
investigation of the causes of the not unfrequently observed ‘spon- 
taneous’ total stoppage of the meridional rows lasting for a few 
seconds. It is equally conceivable that these spontaneous stop- 
pages without any retraction of the rows may arise from a 
momentary cessation of the vibrations of the balancers or that 
they are due to an invisible stimulation, brought about by chemi- 
cal or osmotic action, of the receptors of the primary inhibitory 
apparatus. 
A common ecological significance of the two mechanisms for 
inhibition of the ciliary motion in Beroé consists in the fact that 
certain external stimuli impart through the mediation of these 
mechanisms a compulsory and important influence on the speed 
and direction of the animal’s movements. 
Two of the principal results of the investigation have a general 
physiological bearing and are consequently of interest apart from 
the species of the animal with which they have been obtained. 
One is that a movement which has all the main characteristics of 
