_Discussion of proposed Regions._--Before proceeding to define the regions adopted in this work, it may be as well to make a few remarks on some of the preceding classifications, and to give the reasons which seem to render it advisable to adopt very few of the suggested improvements on Mr. Sclater's original proposal. Mr. Blyth's scheme is one of the least natural, and also the most inconvenient. There can be little use in the knowledge that a group of animals is found in the Boreal Region, if their habitat might still be either Patagonia, the West Indies, or Japan; and it is difficult to see on what principle the Madagascar group of islands is made of equal rank with this enormous region, seeing that its forms of life have marked African affinities. Neither does it seem advisable to adopt the Polynesian Region, or that comprising New Zealand alone (as hinted at by Professor Huxley and since adopted by {62}Mr. Sclater in his Lectures on Geographical Distribution at the Zoological Gardens in May 1874), because it is absolutely without indigenous mammalia and very poor in all forms of life, and therefore by no means prominent or important enough to form a primary region of the earth. It may be as well here to notice what appears to be a serious objection to making New Zealand, or any similar isolated district, one of the great zoological regions, comparable to South America, Australia, or Ethiopia; which is, that its claim to that distinction rests on grounds which are liable to fail. It is because New Zealand, in addition to its negative merits, possesses three families of birds (Apterygidæ living, Dinornithidæ and Palapterygidæ extinct), and a peculiar lizard-like reptile, _Hatteria_, which has to be classed in a distinct order, Rhynchocephalina, that the rank of a Region is claimed for it. But supposing, what is not at all improbable, that other Rhynchocephalina should be discovered in the interior of Australia or in New Guinea, and that Apterygidæ or Palapterygidæ should be found to have inhabited Australia in Post-Pliocene times, (as Dinornithidæ have already been proved to have done) the claims of New Zealand would entirely fail, and it would be universally acknowledged to be a part of the great Australian region. No such reversal can take place in the case of the other regions; because they rest, not upon one or two, but upon a large number of peculiarities, of such a nature that there is no room upon the globe for discoveries that can seriously modify them. Even if one or two peculiar types, like Apterygidæ or _Hatteria_, should permanently remain characteristic of New Zealand alone, we can account for these by the extreme isolation of the country, and the absence of enemies, which have enabled these defenceless birds and reptiles to continue their existence; just as the isolation and protection of the caverns of Carniola have enabled the _Proteus_ to survive in Europe. But