A study has been made on the effects of acid, alkali and voltage to the adhesive force of Purpura ciavigera, with ?? view to eliminate the oyster drills out of the seed oysters.
The study has been carried out under the same method employed in my previous investigation4). The media used herein are as follows: Acidified sea water was prepared by adding hydrochloric acid (35% HCl) at the rate of 0.10, 0.20-0.25, 0.30, 0.67 and 3.00cc. per litre of sea water respectively. Alkalified one was set by addition of ammonia (28% NH3) at the rate of 0.01, 0.05, 0.10, 0.15 and 0.20cc. per litre of sea water respectively. In the experiment of electrifing the drills, ?? glass jar, 11×16×23cm. in size, was used. An abalone shell with drills firmly attached on it was suspended vertically in the jar filled with three litres of sea water, 15.8-16.2°C. in temperature. Carbon electrodes taken from dry cells were set down on each side of the abalone shell at a distance of ten centimetres. Voltages from 10 to 80 were tested.
The results obtained are as follows. The adhesive force of the drill seems to be weak against alkali and electricity, while it seems to stand surprisingly against acid. Besides these, it should be mentioned herewith that the percentage of drills fallen off is hundred per cent in the annexed cases: pH 9.4 (29.9°C.) and 1.5 (30.0, 15.6, 3.6°C.), and voltages above 70 (16.0°C.).