494 
KEELING ISLAND 
CHAP. 
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 
Ehrenberg to be partly composed of sihceous-shielded infusoria. 
April 12th .—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, 1 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 
1 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. 
