_Comparison of Zoological Regions with the Geographical Divisions of the Globe._--Having now completed our survey of the great zoological regions of the globe, we find that they do not differ so much from the old geographical divisions as our first example might have led us to suppose. Europe, Asia, Africa, Australia, North America, and South America, really correspond, each to a zoological region, but their boundaries require to be modified more or less considerably; and if we remember this, and keep their extensions or limitations always in our mind, we may use the terms "South American" or "North American," as being equivalent to Neotropical and Nearctic, without much inconvenience, while "African" and "Australian" equally well serve to express the zoological type of the Ethiopian and Australian regions. Europe and Asia require more important modifications. The European fauna does indeed well represent the Palaearctic in all its main features, and if instead of Asia we say tropical Asia we have the Oriental region very fairly defined; so that the relation of the geographical with the zoological primary divisions of the earth is sufficiently clear. In order to make these relations visible to the eye and more easily remembered, we will put them into a tabular form: Regions. Geographical Equivalent. Palaearctic EUROPE, with north temperate Africa and Asia. Ethiopian AFRICA (south of the Sahara) with Madagascar. Oriental TROPICAL ASIA, to Philippines and Java. Australian AUSTRALIA, with Pacific Islands, Moluccas, &c. Nearctic NORTH AMERICA, to North Mexico. Neotropical SOUTH AMERICA, with tropical N. America and W. Indies. The following arrangement of the regions will indicate their geographical position, and to a considerable extent their relation to each other. N E A R C T I C--P A L A E A R C T I C | | | | | ORIENTAL | ETHIOPIAN | NEO- | TROPICAL AUSTRALIAN May 4th. Diameter of spot 31deg 24' June 4th. ,, ,, 28deg 0' ,, 17th. ,, ,, 22deg 54' July 4th. ,, ,, 18deg 24' ,, 12th. ,, ,, 15deg 20' ,, 20th. ,, ,, 18deg 0' We thus see that Mars has two permanent snow-caps, of nearly equal size in winter but diminishing very unequally {55} in summer, when the southern cap is reduced to nearly one third the size of the northern; and this fact is held by Mr. Carpenter, as it was by the late Mr. Belt, to be opposed to the view of the hemisphere which has winter in _aphelion_ (as the southern now has both in the Earth and Mars), having been alone glaciated during periods of high excentricity.[9]