494 KEELING ISLAND 



of the Astrolabe, that an Actinia or sea-anemone, as well as a 

 flexible coralline allied to Sertularia, both possess this means 

 of offence or defence. In the East Indian sea a stinging sea- 

 weed is said to be found. 



Two species of fish, of the genus Scarus, which are common 

 here, exclusively feed on coral ; both are coloured of a splendid 

 bluish-green, one living invariably in the lagoon, and the other 

 amongst the outer breakers. Mr. Liesk assured us that he had 

 repeatedly seen whole shoals grazing with their strong bony 

 jaws on the tops of the coral branches ; I opened the intestines 

 of several and found them distended with yellowish calcareous 

 sandy mud. The slimy disgusting Holothuriae (allied to our 

 star-fish), which the Chinese gourmands are so fond of, also 

 feed largely, as I am informed by Dr. Allan, on corals ; and 

 the bony apparatus within their bodies seems well adapted for 

 this end. These holothuriae, the fish, the numerous burrowing 

 shells, and nereidous worms, which perforate every block of 

 dead coral, must be very efficient agents in producing the fine 

 white mud which lies at the bottom and on the shores of the 

 lagoon. A portion, however, of this mud, which when wet 

 strikingly resembled pounded chalk, was found by Professor 

 Ehienberg to be partly composed of siliceous-shielded infusoria. 



April 12///.— In the morning we stood out of the lagoon 



on our passage to the Isle of France. I am glad we have 



visited these islands : such formations surely rank high amongst 



the wonderful objects of this world. Captain Fitz Roy found 



no bottom with a line 7200 feet in length, at the distance of 



only 2200 yards from the shore; hence this island forms a 



lofty submarine mountain, with sides steeper even than those 



of the most abrupt volcanic cone. The saucer-shaped summit 



is nearly ten miles across ; and every single atom,^ from the 



least particle to the largest fragment of rock, in this great pile, 



which however is small compared with very many other lagoon 



islands, bears the stamp of having been subjected to organic 



arrangement. We feel surprise when travellers tell us of the 



vast dimensions of the Pyramids and other great ruins, but how 



utterly insignificant are the greatest of these, when compared 



^ I exclude, of course, some soil which has been imported here in vessels from 

 Malacca and Java, and likewise some small fragments of pumice, drifted here by the 

 waves. The one block of greenstone, moreover, on the northern island must be 

 excepted. 



