The Cassowary Is Distinct; The Kingfishers, Parrots, Pigeons, Flycatchers, Honeysuckers, Thrushes, And Cuckoos, Are Almost Always Quite Distinct Species. More

Than this, at least twenty genera, which are common to New Guinea and Aru, do not extend into Ceram, indicating

With a force which every naturalist will appreciate, that the two latter countries have received their faunas in a radically different manner. Again, a true kangaroo is found in Aru, and the same species occurs in Mysol, which is equally Papuan in its productions, while either the same, or one closely allied to it, inhabits New Guinea; but no such animal is found in Ceram, which is only sixty miles from Mysol. Another small marsupial animal (Perameles doreyanus) is common to Aru and New Guinea. The insects show exactly the same results. The butterflies of Aru are all either New Guinea species, or very slightly modified forms; whereas those of Ceram are more distinct than are the birds of the two countries.

It is now generally admitted that we may safely reason on such facts as those, which supply a link in the defective geological record. The upward and downward movements which any country has undergone, and the succession of such movements, can be determined with much accuracy; but geology alone can tell us nothing of lands which have entirely disappeared beneath the ocean. Here physical geography and the distribution of animals and plants are of the greatest service. By ascertaining the depth of the seas separating one country from another, we can form some judgment of the changes which are taking place. If there are other evidences of subsidence, a shallow sea implies a former connexion of the adjacent lands; but i£ 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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