Perhaps it would be well to explain exactly what is meant by an animal or a plant zone. In making a faunal or floral survey of a wide expanse of territory, say, a land-mass like that of Asia and Europe, it is found that each of the various species of animals and plants has a certain well defined range, occupies a certain definite area. If these were to be outlined on pieces of paper in correct proportion to one another, and then were cut out and placed one after the other on a map of the same scale, it would be discovered that they would fall into groups or series. Thus there would be a whole series covering an area running roughly along the coast from of Region, and, as such, may be accepted, although it should be noted that within them are smaller well defined sub-regions or zones, as already outlined, and which may be named for the purposes of this discussion the Arctic or Circumpolar Subregion, the Euro-Siberian Sub-region, the Tartarian Sub-region and the Sinian or Chinese Sub-region.
It should be noted that the outlines of these zones are not sharply defined (although the boundaries of the range of each species or genus belonging to them may be), but are rather hazy and merge more or less imperceptibly into each other. A little way from their meeting and merging lines, however, they become very distinct.
Text read from the printed page and cleaned; old type leaves the occasional error.