THE CEILING OF THE BAY 



began searching for rare fish and found as usual 

 that all kinds except wrasse had succumbed. 



At last I climbed up, and, after an interval, again 

 dived. Most of the tinsel fish had disappeared 

 from the reef floor, not, as I first thought, all 

 devoured by larger fish, but resurrected, gathered 

 in dense masses in mid-water, swimming so closely 

 together that each group was opaque. Three 

 great mobs of fishlets were milling about, not only 

 as regards the whole, but each individual slowly 

 turning on its own axis, not very fast but rather 

 regularly. 



I approached and, to my surprise, found that 

 they did not move away. I put my hand among 

 them and touched many as it was moved to and fro. 

 I caught several in my hand. 



I climbed part way up the ladder and signalled 

 for a net, and by moving it slowly back and 'forth, 

 in three sweeps I captured one thousand and fifty- 

 three of three species — silversides and herringlets. 

 This made no impression whatever on the general 

 numbers and I watched one very interesting event. 

 This was the approach of two swarms — in their 

 present condition they deserved no other name. 

 The two came slowly together and partly coalesced, 

 and then again separated. Each was made up of 

 the same small species, but each was milling at 

 different rates, and the two masses actually met 

 and passed through one another without losing 

 their individuality or general numbers or direction. 

 It seemed as if the slight difference in reaction 



31 



