THE HEARING OF SEA-FISH LARViTl. 85 



of transferring larva? four or five days old from a plunger-jar to a jar of 

 stagnant water, devoid of a plunger, and aerated by means of green 

 algse exposed to direct sunlight immediately in front of a south window. 

 The jar was broader than the rearing jars, and of different shape, having 

 a flat bottom and cylindrical sides, and terminating above in a shoulder 

 and a neck about 3 inches in diameter. It contained about 3 gallons 

 when full, but was not filled during the first few weeks beyond 

 about two-thirds or three-quarters of its total height. It was immersed 

 to a little below the same height in a tank of circulating water in the 

 full blaze of the midday and afternoon sun. The current in the outer 

 tank was not strong enough to keep the temperature in the jar constant, 

 but served to moderate it. The following series of temperatures give 

 an idea of the range of temperature to which the larvae were exposed : — 



As shown by the figures, the uppermost layer of water in the jar was 

 generally warmer than the rest during the daytime, since the outer 

 jacket of circulating water was not high enough to surround it; and 

 the amount of the excess depended on the sunshine, amounting to 

 2|° C. on hot afternoons {e.g. August 26th) or of a mere fraction of 

 a degree on cloudy days (August 27th, September 2nd). The bottom 

 temperature amounted to 22°-0 at 4 p.m. on August 23rd, but rarely 

 exceeded 21°-0 after the first few days. 



A small tuft of Edocarpus was placed at the bottom of the jar under 

 a small glass funnel as a means of aerating and purifying the water. 

 During sunshine the small bubbles of oxygen emitted by the plant 

 escaped into the surrounding water in a continuous stream through the 

 narrow aperture of the funnel ; and in a very short time the bottom and 

 sides of the jar became covered with a perfect jungle of the same alga 

 from the fixation and development of the spores liberated by the 

 original tuft, which, with the funnel, was then removed. 



Into this jar, on August 22nd, were placed six larvae derived from the 

 same batch of eggs as those in experiments F and G, but they were 

 already from four to five days old at the time of their introduction. 

 Previous to this they had been kept in a plunger-jar (E) under the 

 same external conditions as F and G. They had not, however, received 

 much attention. The six larvas were the survivors of ten or eleven 

 which had been isolated on the 18th (from twelve to twenty-four hours 

 after hatching), and had received no change of water and only one 



