If There Are
Other Evidences Of Subsidence, A Shallow Sea Implies A Former
Connexion Of The Adjacent Lands; But IŁ
This evidence is wanting,
or if there is reason to suspect a rising of the land, then the
shallow sea
May be the result of that rising, and may indicate
that the two countries will be joined at some future time, but
not that they have previously been so. The nature of the animals
and plants inhabiting these countries will, however, almost
always enable us to determine this question. Mr. Darwin has shown
us how we may determine in almost every case, whether an island
has ever been connected with a continent or larger land, by the
presence or absence of terrestrial Mammalia and reptiles. What he
terms "oceanic islands "possess neither of these groups of
animals, though they may have a luxuriant vegetation, and a fair
number of birds, insects, and landshells; and we therefore
conclude that they have originated in mid-ocean, and have never
been connected with the nearest masses of land. St. Helena,
Madeira, and New Zealand are examples of oceanic islands. They
possess all other classes of life, because these have means of
dispersion over wide spaces of sea, which terrestrial mammals and
birds have not, as is fully explained in Sir Charles Lyell's
"Principles of Geology," and Mr. Darwin's "Origin of Species." On
the other hand, an island may never have been actually connected
with the adjacent continents or islands, and yet may possess
representatives of all classes of animals, because many
terrestrial mammals and some reptiles have the means of passing
over short distances of sea.
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