PRIMARY INHIBITION OF CILIARY MOVEMENT 423 
With five elements. While the negative electrode is situated 
outside the end of the sensory pole of the preparation and the 
latter shows a comparatively rapid spontaneous ciliary vibration, 
the current is closed. The nine swimming plates nearest to the 
cathode then stop, while the twelve nearest to the anode con- 
tinue to vibrate. The current is then broken. 
After a short pause and after the direction of the current has 
been reversed, a current is sent through the preparation while 
the vibration still continues. Then the nine swimming plates 
that are now situated nearest to the cathode (i.e., plates quite 
different from the previous ones) stop, while the ciliary motion 
continues in the twelve that are nearest to the anode. 
11. A Beroé, 18 mm. long, is investigated at a temperature of 
16°. The animal keeps to the bottom of the cuvette in the usual 
horizontal position. While the ciliary action continues the ani- 
mal glides along the bottom of the cuvette. It is observed that 
the ciliary activity is slower on the rows that are situated below 
the meridian plane through the points of the polar fields than on 
those that are above this plane. With the help of glass rods with 
round ends the animal is carefully moved into such a position 
that the same meridian as before remains horizontal, but that 
the half of the animal that previously faced downward now 
faces upward, and vice versa. In this position, too, i.e., after a 
turn of 180°, the rows that face downward have a less frequent 
ciliary action than those that face upwards. The animal is 
restored to its former position in thesame way. After thisis done 
the rows on the half of the body that is lowest show once more a 
slower ciliary motion. | 
The same observations were made on several different occa- 
sions and with several different animals. 
On one occasion when a Beroé 24 mm. long is observed in the 
usual horizontal position at the bottom of the cuvette at a 
temperature of 16.7°; an attempt is made with a stop-watch 
to count the frequency in the upper and lower rows. On the 
lower rows thirty-nine waves in 45 seconds are reckoned (= 52 
per minute); on the upper ones the number of waves cannot 
generally be counted with the naked eye, and in any case it is 
