The geographical distribution of animals, with a study of the relations ...

214 ZOOLOGICAL GEOGRAPHY. [part hi.nected with Europe at a farremoter epoch, and ought thereforeto exhibit to us. a fauna composed almost entirelyforms both of birds and insects.of peculiarYet, so far from this being thecase, the facts are exactly the reverse. Far more of the birdsand insects are identical with those of Europe than in theother islands, and this difference is clearly traced to the moretempestuous atmosphere, which is shown to be even nowannually bringing fresh immigrants (both birds and insects) toits shores. We here see nature actually at work ; and if thecase of Madeira rendered her mode of action probable, that ofthe Azores may be saidto demonstrate it.Mr. Wollaston has objected to this view that " storms andhurricanes " are somewhat rare in the latitude of Madeira andthe Canaries ; but this little affects the question, since the timeallowed for such operations is so ample. If but one veryviolent storm happened in a century, and ten such stormsrecurred before a single species of insect was introduced intoMadeira, that would be more than sufficient to people it, as wenow find it, with a varied fauna. But he also adds the importantinformation that the ordinary winds blow almost uninterruptedlyfrom the north-east, so that there would be always achance of a little stronger wind than usual bringing insect, orlarva, or egg, attached to leaves or twigs. Neither Mr. Wollaston,Mr. Crotch, Mr. A. Murray, nor any other naturalist whoupholds the land-connection theory, has attempted to accountfor the fact of the absence of so many extensive groups ofinsects that ought to be present, as well as of all smallmammalia and reptiles.Cape Vera 1 Islands.—There is yet another group of Atlanticislands which is very little known, and which is usually consideredto be altogether African—the Cape Verd Islands, situatedbetween 300 and 400 miles west of Senegal, and a little to thesouth of the termination of the Sahara. The evidence that wepossess as to the productions of these islands, shows that, likethe preceding groups, they are truly oceanic, and have probablyderived their fauna from the desert and the Canaries to thenorth-east of them rather than from the fertile and more truly