(Machaerirhynchus); and the elegant blue flycatcher-wrens (Todopsis).
The naturalist will obtain a clearer idea of the variety and interest of the
productions of this country, by the statement, that its land birds belong to 108
genera, of which 20 are exclusively characteristic of it; while 35 belong to that
limited area which includes the Moluccas and North Australia, and whose
species of these genera have been entirely derived from New Guinea. About
one-half of the New Guinea genera are found also in Australia, about one-third
in India and the Indo-Malay islands.
A very curious fact, not hitherto sufficiently noticed, is the appearance of a
pure Malay element in the birds of New Guinea. We find two species of Eupetes,
a curious Malayan genus allied to the forked-tail water-chats; two of Alcippe, an
Indian and Malay wren-like form; an Arachnothera, quite resembling the spider-
catching honeysuckers of Malacca; two species of Gracula, the Mynahs of India;
and a curious little black Prionochilus, a saw-billed fruit pecker, undoubtedly
allied to the Malayan form, although perhaps a distinct genus. Now not one of
these birds, or anything allied to them, occurs in the Moluccas, or (with one
exception) in Celebes or Australia; and as they are most of them birds of short
flight, it is very difficult to conceive how or when they could have crossed the
space of more than a thousand miles, which now separates them from their
nearest allies. Such facts point to changes of land and sea on a large scale, and at
a rate which, measured by the time required for a change of species, must be
termed rapid. By speculating on such changes, we may easily see how partial
waves of immigration may have entered New Guinea, and how all trace of their
passage may have been obliterated by the subsequent disappearance of the
intervening land.
There is nothing that the study of geology teaches us that is more certain or
more impressive than the extreme instability of the earth's surface. Everywhere
beneath our feet we find proofs that what is land has been sea, and that where
oceans now spread out has once been land; and that this change from sea to land,
and from land to sea, has taken place, not once or twice only, but again and
again, during countless ages of past time. Now the study of the distribution of
animal life upon the present surface of the earth, causes us to look upon this
constant interchange of land and sea—this making and unmaking of continents,
this elevation and disappearance of islands—as a potent reality, which has
always and everywhere been in progress, and has been the main agent in
determining the manner in which living things are now grouped and scattered
over the earth's surface. And when we continually come upon such little
anomalies of distribution as that just now described, we find the only rational