Geological researches into the structure of the globe show that a succession of physical changes have modified its surface from the earliest period up to the present time, and that these changes have been accompanied with variations not only in the phases of animal and vegetable life, but often in the development also of organization; and as these changes cannot be supposed to have been operating uniformly over the entire surface of the globe in the same periods of time, we should naturally be prepared for finding the now existing fauna of some regions exhibiting a higher state of development than that of others; accordingly, if we contrast the fauna of the old continents of geographers with the zoology of Australia and New Zealand, we find a wide difference in the degree of organization which creation has reached in these respective regions. In New Zealand, with the exception of a _Vespertilio_ and a _Mus_, which latter is said to exist there, but which has not yet been sent to this country, the most highly organized animal hitherto discovered, either fossil or recent, is a bird; in Australia, if compared with New Zealand, creation appears to have considerably advanced, but even here the order _Rodentia_ is the highest in the scale of its indigenous animal productions; the great majority of its quadrupeds being the MARSUPIATA (Kangaroos, &c.) and the MONOTREMATA (_Echidna_ and _Ornithorhynchus_), which are the very lowest of the Mammalia; and its ornithology being characterized by the presence of certain peculiar genera, _Talegalla_, _Leipoa_ and _Megapodius_; birds which do not incubate their own eggs, and which are perhaps the lowest representatives of their class, while the low organization of its botany is indicated by the remarkable absence of fruit-bearing trees, the _Cerealia_, &c.