270 DAHLAK 



quickly that I could hardly follow them with my eyes; not 

 one of them could be distinguished from the coral ; it was 

 just as if each one had his own particular camouflage for a 

 certain branch of the block. When I took my hand away 

 again they came out of hiding, so it would seem that the 

 association bet\veen the two was not for food but for defence, 

 a view which was confirmed by practical demonstration some 

 days later. One of my colleagues was hauling up a large 

 block of madrepore from the sea-floor when an imprudent 

 pomacentrid jumped out from its branch and tried to regain 

 the bottom in search of a more secure stronghold. Vain hope. 

 In spite of flappings and twistings he had hardly got more 

 than two yards away (the speed of these fish is very limited) 

 when he was torn to pieces by a smaller grouper and some 

 other plunderers faster than he. The other pomacentrids that 

 stayed behind in the ramifications of the madrepore had 

 no better a fate; they died of asphyxia as the sun dried the 

 block into brilliant iridescence at the bottom of the boat. 

 The atavistic instinct of these fish does not survive the 

 removal of their stronghold from its aquatic environment. 



Wishing to confirm the hypothesis that big jaws consti- 

 tuted their main peril, I found a large tenanted madrepore, 

 shook it violently to drive out the fish, and left these free to 

 reach the coral floor. A crowd of small grouper and bream 

 immediately pounced on them and only three of them, by 

 grace of the sacrifice of their fellows, succeeded in reaching 

 the safety of new crevices. Poor little fish, life is impossible 

 for them without their coral hiding-place. 



