Page:Darwin Journal of Researches.djvu/32

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10
[chap. i.
ST. PAUL'S ROCKS.

shells, of all living animals, it is an interesting physiological fact[1] to find substances harder than the enamel of teeth, and coloured surfaces as well polished as those of a fresh shell, reformed through inorganic means from dead organic matter—mocking, also, in shape some of the lower vegetable productions.

We found on St. Paul's only two kinds of birds—the booby and the noddy. The former is a species of gannet, and the latter a tern. Both are of a tame and stupid disposition, and are so unaccustomed to visitors, that I could have killed any number of them with my geological hammer. The booby lays her eggs on the bare rock ; but the tern makes a very simple nest with seaweed. By the side of many of these nests a small flying-fish was placed ; which, I suppose, had been brought by the male bird for its partner. It was amusing to watch how quickly a large and active crab (Graspus), which inhabits the crevices of the rock, stole the fish from the side of the nest, as soon as we had disturbed the parent birds. Sir W. Symonds, one of the few persons who have landed here, informs me that he saw the crabs dragging even the young birds out of their nests, and devouring them. Not a single plant, not even a lichen, grows on this islet; yet it is inhabited by several insects and spiders. The following list completes, I believe, the terrestrial fauna : a fly (Oliersia) living on the booby, and a tick which must have come here as a parasite on the birds ; a small brown moth, belonging to a genus that feeds on feathers ; a beetle (Quedius) and a woodlouse from beneath the dung ; and lastly, numerous spiders, which I suppose prey on these small attendants and scavengers of the waterfowl. The often repeated description of the stately palm and other noble tropical plants, then birds, and lastly man, taking possession of the coral islets as soon as formed, in the Pacific, is probably not quite correct; I fear it destroys the poetry of this story, that feather and dirt-

  1. Mr. Horner and Sir David Brewster have described (Philosophical Transactions, 1836, p. 65) a singular “artificial substance resembling shell.” It is deposited in fine, transparent, highly polished, brown-coloured laminæ, possessing peculiar optical properties, on the inside of a vessel, in which cloth, first prepared with glue and then with lime, is made to revolve rapidly in water. It is much softer, more transparent, and contains more animal matter, than the natural incrustation at Ascension ; but we here again see the strong tendency which carbonate of lime and animal matter evince to form a solid substance allied to shell.