426 GUSTAF FR. GOTHLIN 
tissue now constitutes the bottom of a cavity, at the edges of 
which the meridional rows begin with slight asymmetry in their 
arrangement. The animal shows a quite uninterrupted ciliary 
activity with a rapid frequency. During this it whirls around 
in the aquarium instead of moving in a more extended course, 
as does a normal animal. There are scarcely more than mere 
indications of spontaneous stoppage. 
2/8. Today a few ‘spontaneous’ total stoppages without any 
retraction of the rows are observed. The animal sometimes rises 
into-a vertical position with its sensory pole upward, but cannot 
maintain this position, striking over in the opposite direction. 
Even if one gives the animal the vertical position just mentioned, 
it appears to be unable to maintain it. 
3/8. 2h. 15 m. No wound cavity is now perceptible on 
examination with a Zeiss binocular lens; the former cavity has 
been quite filled up with a red-pigmented fimbriated tissue. 
Total inhibition of the meridional rows can now be brought 
about by touching the edges of the animal’s mouth; it is accom- 
panied by such a slight retraction of the rows that this cannot 
produce stoppage in a mechanical way. The animal still shows 
in the horizontal position no constant difference between the 
rapidity of vibration in the upper and lower rows. 
DISCUSSION OF THE RESULTS OF THE EXPERIMENTS. 
THEORETICAL CONSIDERATIONS 
In the preceding chapter experiments have been described 
which indicate that primary total stoppage of the swimming: 
plates in Beroé ean be produced either by mechanical, electrical 
or chemical stimuli. I shall first discuss in more detail the 
special circumstances under which each of these different stimuli 
showed itself to be effective. 
In experiments 4 and 12 it is shown—an observation which as 
a matter of fact was made on many occasions with different indi- 
viduals—that mechanical stimulation of the edges of the mouth 
and also mechanical stimulation of the polar fields caused stop- 
page of the swimming plates without any retraction of the rows. 
