CHAP. II.] MADE IE A TO THE COAST OF BRAZIL. 97 



neither of which we detected. All the insects and Arachnida 

 were found in the old nests of the tern, many of which were 

 brought on board and carefully examined. 



There is not a trace of a land-plant on this island- — not even 

 a lichen. In the line within the wash of the surf there is a 

 bright -pink band of an incrusting nullipore, which here and 

 there becomes white, and greatly resembles a coral ; and the 

 same belt j^roduces the conferva of which the terns' nests are 

 built, and one or two red algae. All the crannies in the rock 

 are inhabited by Grapsus strigosus, an amphibious crab, which 

 we had already met with on several of the Atlantic islands. Its 

 habits amused us greatly. It was much more wary than the 

 birds. It was by no means easy to catch them, but they kept 

 close round the luncheon baskets in large parties, raised up on 

 the tips of their toes, and with their eyes cocked up in an atti- 

 tude of the keenest observation ; and whenever a morsel came 

 within their reach there was instantly a struggle for it among 

 the foremost of them, and they ambled away with their prize 

 wonderfully quickly, with their singular sidelong gait, and a 

 look of human smartness about them wliicli has a kind of weird- 

 ness from its being exhibited through a set of organs totally 

 different in aspect from those to which we usually look for 

 manifestations of intelligence. 



The lobster -pots were down during the night, but they 

 yielded little except a small species of Palinurus. 



The structure of the rocks is j^eculiar, and they must be care- 

 fully analyzed before any definite opinion can be arrived at 

 with regard to them. They are certainly, as Mr. Darwin has 

 already pointed out, not of modern volcanic origin, like almost 

 all the other ocean islands. They look more like the serpenti- 

 nous rocks of Cornwall or Ayrshire, l)ut from these even they 

 differ greatly in character. Mr. Buchanan examined their min- 

 eral character carefully, and subjected the most marked varie- 

 ties to a I'ough chemical analysis. I quote from his notes. The 



