E.V. Harcourt, many European and African birds are blown to Madeira;
this island is inhabited by ninety-nine kinds, of which one alone is
peculiar, though very closely related to a European form; and three or four
other species are confined to this island and to the Canaries. So that the
islands of Bermuda and Madeira have been stocked from the neighbouring
continents with birds, which for long ages have there struggled together,
and have become mutually co-adapted. Hence, when settled in their new
homes, each kind will have been kept by the others to its proper place and
habits, and will consequently have been but little liable to modification.
Any tendency to modification will also have been checked by intercrossing
with the unmodified immigrants, often arriving from the mother-country.
Madeira again is inhabited by a wonderful number of peculiar land-shells,
whereas not one species of sea-shell is peculiar to its shores: now,
though we do not know how sea-shells are dispersed, yet we can see that
their eggs or larvae, perhaps attached to seaweed or floating timber, or to
the feet of wading birds, might be transported across three or four hundred
miles of open sea far more easily than land-shells. The different orders
of insects inhabiting Madeira present nearly parallel cases.
Oceanic islands are sometimes deficient in animals of certain whole
classes, and their places are occupied by other classes; thus in the
Galapagos Islands reptiles, and in New Zealand gigantic wingless birds,
take, or recently took, the place of mammals.
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