Island Life; Or, The Phenomena and Causes of Insular Faunas and Floras. Alfred Russel WallaceЧитать онлайн книгу.

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the great scientific voyages of the various civilized governments during the present century. All these expeditions combined have done far less than private collectors in making known the products of remote lands and islands. They have brought home fragmentary collections, made in widely scattered localities, and these have been usually described in huge folios or quartos, whose value is often in inverse proportion to their bulk and cost. The same species have been collected again and again, often described several times over under new names, and not unfrequently stated to be from places they never inhabited. The result of this wretched system is that the productions of some of the most frequently visited and most interesting islands on the globe are still very imperfectly known, while their native plants and animals are being yearly exterminated, and this is the case even with countries under the rule or protection of European governments. Such are the Sandwich Islands, Tahiti, the Marquesas, the Philippine Islands, and a host of smaller ones; while Bourbon and Mauritius, St. Helena, and several others, have only been adequately explored after an important portion of their productions has been destroyed by cultivation or the reckless introduction of goats and pigs. The employment in each of our possessions, and those of other European powers, of a resident naturalist at a very small annual expense, would have done more for the advancement of knowledge in this direction than all the expensive expeditions that have again and again circumnavigated the globe.

3

The general facts of Palæontology, as bearing on the migrations of animal groups, are summarised in my Geographical Distribution of Animals, Vol. I. Chapters VI., VII., and VIII.

4

Since these lines were written, a fine series of specimens of this rare humming-bird has been obtained from the same locality. (See Proc. Zool. Soc. 1881, pp. 827-834.)

5

Many of these large genera are now subdivided, the divisions being sometimes termed genera, sometimes sub-genera.

6

The Palæarctic region includes temperate Asia and Europe, as will be explained in the next chapter.

7

The following list of the genera of reptiles and amphibia peculiar to the Palæarctic Region has been furnished me by Mr. G. A. Boulenger, of the British Museum:—

8

Remains of the dingo have been found fossil in Pleistocene deposits but the antiquity of man in Australia is not known. It is not, however, improbable that it may be as great as in Europe. My friend A. C. Swinton, Esq., while working in the then almost unknown gold-field of Maryborough, Victoria, in January, 1855, found a fragment of a well-formed stone axe resting on the metamorphic schistose bed-rock about five feet beneath the surface. It was overlain by the compact gravel drift called by the miners "cement," and by an included layer of hard iron-stained sandstone. The fragment is about an inch and three-eighths wide and the same length, and is of very hard fine-grained black basalt. One side is ground to a very smooth and regular surface, terminating in a well-formed cutting edge more than an inch long, the return face of the cutting part being about a quarter of an inch wide. The other side is a broken surface. The weapon appears to have been an axe or tomahawk closely resembling that figured at p. 335 of Lumholtz's Among Cannibals, from Central Queensland. The fragment was discovered by Mr. Swinton and the late Mr. Mackworth Shore, one of the discoverers of the gold-field, before any rush to it had taken place, and it seems impossible to avoid the conclusion that it was formed prior to the deposit of the gravel drift and iron-stained sandstone under which it lay. This would indicate a great antiquity of man in Australia, and would enable us to account for the fossilised remains of the dingo in Pleistocene deposits as those of an animal introduced by man.

9

These facts are taken from a memoir on The Mammals and Winter Birds of Florida, by J. A. Allen; forming Vol. II., No. 3, of the Bulletin of the Museum of Comparative Zoology at Harvard College, Cambridge, Massachusetts.

10

The great variation in wild animals is more fully discussed and illustrated in the author's Darwinism (Chapter III.).

11

See Ibis, 1879, p. 32.

12

In Mr. Seebohm's latest work, Birds of the Japanese Empire (1890), he says, "Examples from North China are indistinguishable from those obtained in Greece" (p. 82).

13

Ibis, 1879, p. 40. In his Birds of the Japanese Empire (1890), Mr. Seebohm classes the Japanese and European forms as E. schœniclus, and thinks that their range is probably continuous across the two continents.

14

Lyell's Principles of Geology, ii., p. 369.

15

Mr. Darwin found that the large Helix pomatia lived after immersion in sea-water for twenty days. It is hardly likely that this is the extreme limit of their powers of endurance, but even this would allow of their being floated many hundred miles at a stretch, and if we suppose the shell to be partially protected in the crevice of a log of wood, and to be thus out of water in calm weather, the distance might extend to a thousand miles or more. The eggs of fresh-water mollusca, as well as the young animals, are known to attach themselves to the feet of aquatic birds, and this is probably the most efficient cause of their very wide diffusion.

16

Principles of Geology, 11th Ed., Vol. I., p. 258.

17

On Limestone as an Index of Geological Time.

18

In his Preliminary Report on Oceanic Deposit, Mr. Murray says:—"It has been found that the deposits taking place near continents and islands have received their chief characteristics from the presence of the debris of adjacent lands. In some cases these deposits extend to a distance of over 150 miles from the coast." (Proceedings of the Royal Society, Vol. XXIV. p. 519.)

"The materials in suspension appear to be almost entirely deposited within 200 miles of the land." (Proceedings of the Royal Society of Edinburgh, 1876-77, p. 253.)

19

Geographical Evolution. (Proceedings of the Royal Geographical Society. 1879, p. 426.)

20

Professor Dana was, I believe, the first to point out that the regions which, after long undergoing subsidence and accumulating vast piles of sedimentary deposit have been elevated into mountain ranges, thereby become stiff and unyielding, and that the next depression and subsequent upheaval will be situated on one or the other sides of it; and he has shown that, in North America, this is the case with all the mountains of the successive geological formations. Thus, depressions, and elevations of extreme slowness but often of vast amount, have occurred successively in restricted adjacent areas; and the effect has been to bring each portion in succession beneath the ocean but always bordered on one or both sides by the remainder of the continent, from the denudation of which the deposits are formed which, on the subsequent upheaval, become mountain ranges. (Manual of Geology, 2nd Ed., p. 751.)

21

Nature, Vol. II., p. 297.

22

Sir W. Thomson, Voyage of Challenger, Vol. II., p. 374.

23

The following is the analysis of the chalk at Oahu:—

This chalk consists simply of comminuted corals and shells of the reef. It has been examined microscopically and found to be destitute of the minute organisms abounding in the chalk of England. (Geology of the United States Exploring Expedition, p. 150.) Mr. Guppy also found chalk-like coral limestones containing 95 p.c. of carbonate of lime in the Solomon Islands.

The absence of Globigerinæ is a local phenomenon. They are quite absent in the Arafura Sea, and no Globigerina-ooze was found in any of the enclosed seas of the Pacific, but with these exceptions the Globigerinæ "are really found all over the bottom of the ocean." (Murray on Oceanic Deposits—Proceedings of Royal Society, Vol. XXIV., p. 523.)

The above analysis shows a far closer resemblance to chalk than that of the Globigerina-ooze

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