Distribution.

If, as seems probable, the rat from all the Pacific Islands is referable to Mus exulans, the range of the species is very great indeed. Considering the native interchange which has taken place between islands hundreds of miles apart for ages past, this is not so remarkable as would at first sight appear.

For a long distance in the West Pacific there runs an enormous chain of islands, extending in a semi-circular sweep from the Marshall Archipelago, north of the equator to the Austral or Tubai Islands in the south-east. Our colleague has written of this as the Marshall-Austral chain, and dealt with it more particularly in his report. ^†

From each of the main links of this long chain of islands, we possess records of the occurrence of a native rat, as below enumerated.

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Wake Island, an isolated atoll, which I would regard as an extension of the chain, is recorded by Peale,¹⁸ and is at the same time the most northerly and westerly (with New Caledonia) rat-inhabited island of which I have notice. Passing southward and westward the rat next appears to have been observed at Odia in the Marshall Group, and is represented by Kotzebue¹⁵ in an illus-tration as impudently trespassing in a Marshall Island house.

Continuing the chain, the rat is recorded from the Gilbert Group by Woodford,²⁵ who remarks that the only wild mammal he met with was a small species of rat common to the islands "in this part of the world."

The next group is that of the Ellice, of which the island of Funafuti at least, is tenanted, and supplied the examples, to be more fully described, and which prompted the present essay.

Mention has previously been made of Savaii being the traditional ancestral home of the Maori rat, but further evidence of its occurrence in Samoa is indicated by the reference to it in ancient tradition detailed by Turner,²³ and direct evidence is afforded²⁴ by this writer in the following note:—"The only indigenous quadruped is a small rat, something between a mouse and the Norwegian rat, the latter of which was introduced some years ago."

The last in the direct chain to which I have reference to the rat is the Cook Group, its occurrence being mentioned at Raratonga and Mangaia by Gill.^{9 &10}

Of localities to the east of the main chain the following have been published. In the Phoenix Group Peale¹⁸ records it from Hull Island, and Arundel² from Sydney Island. Much further to the east it has been met with by Dixon⁷ at Maiden Island, and also further to the south by Lamont, as quoted by Smith²¹ at Penhryn Island, and Dixon⁸ at Caroline Island, all isolated atolls. In the Paumotu Group or Low Archipelago Peale again records it from Disappointment and Dog Islands, and also from the Society Islands, remarking that the species was seen on but one "high" island, Tahiti.

Its north-eastern limit is suggested by a statement by Brigham³ that "Rats and mice have always been a pest on the Hawaiian Islands; and the old Hawaiian, before the introduction of cats, used a bow and arrows to destroy them. It is curious that knowing the principle of the bow they never used it as a weapon of offence, nor developed it beyond a very feeble instrument only suited to the killing of 'rats and mice and such small deer.'"

To the westward of the main chain Allardyce¹ records it from Rotumah, and it is once more mentioned by Peale from Fiji as Mus vitiensis, and from Hoonga in the Tonga Islands by page 169Mariner.¹⁶ The occurrence of a rat in the Kermadec Islands was first recorded by Smith,²⁰ who wrote:—"The only animal native to the island is a small grey rat, which is very plentiful in summer, but is supposed to hybernate during the winter. We saw one that had been partly eaten—by a hawk probably,—it was about five inches long." Thomas also received it from Sunday Island in this group, as already quoted. Away to the west it appears in New Caledonia, and again at Norfolk Island on the authority of Buller,⁵ who states that there are specimens in the British Museum from these localities.

The list of localities is closed by the inclusion of New Zealand as the most southern limit, and to which previous mention has been made in notices by Hutton, Thomas, Hochstetter, and others.

Although a systematic search of the literature of the Pacific Islands would doubtless disclose many more references to the rat, the above are the only definite localities I have so far met with. There is little doubt that the rat exists, or rather did exist, at one time or another on all the islands of the Pacific. Gill⁹ writing in 1876, and mentioning the islands of the South Seas as being inhabited by dogs, hogs, and rats, says:—"The rat alone is universal."

Arundel,² who called at many of the atolls in the Central Pacific, states:—"I have never visited an island, however small or barren, without finding these animals living upon it."