XI 6 Charles Darwin. 



mass to use as junk. It has been stated by some 

 authors that the Birgos crawls up the cocoa-nut trees 

 for the purpose of stealing the nuts ; I very much 

 doubt the possibility of this. I was told by Mr. 

 Liesk that on these islands the Birgos lives only on 

 the nuts which have fallen to the ground. To show 

 the wonderful strength of the front pair of pincers, 

 I may mention that Captain Moresby confined one 

 in a strong tin box, which had held biscuits, the lid 

 being secured with wire ; but the crab turned down 

 the edges and escaped. In turning down the edges 

 it actually punched many small holes quite through 

 the tin ! " 



Among the discomforts of the reef were the sting- 

 ing corals, millepora, the big black echini, whose long 

 slender spines projected everywhere above the sur- 

 face. Among the coral were many fish of resplen- 

 dant colouring, the parrot-fish, or Scarus, attracting 

 Darwin's attention for the reason that it was a coral 

 eater, the jaws being provided with bony ivory-like 

 teeth well adapted for this purpose. Darwin saw in 

 these coral-eating fish, the holothurians that ate mud 

 and ground it up, the worms and shells, the agents 

 which were at work here in lagoon-making, the white 

 deposit of mud being mainly due to them a sug- 

 gestion that has been shown to contain much truth. 



The dredging about Keeling Island was suggestive 

 to Darwin of interesting theories regarding the struc- 

 ture of reefs. Thus he found that at a distance of 

 twenty-two hundred yards from the shore the water 

 suddenly deepened, so that a line over a mile in 

 length found no bottom ; hence he assumed that the 



