The general conclusions regarding the geography of organic nature, may be thus stated. (1.) There are numerous distinct foci of organic production throughout the earth. (2.) These have everywhere advanced in accordance with the local conditions of climate &c., as far as at least the class and order are concerned, a diversity taking place in the lower gradations. No physical or geographical reason appearing for this diversity, we are led to infer that, (3,) it is the result of minute and inappreciable causes giving the law of organic development a particular direction in the lower subdivisions of the two kingdoms. (4.) Development has not gone on to equal results in the various continents, being most advanced in the eastern continent, next in the western, and least in Australia, this inequality being perhaps the result of the comparative antiquity of the various regions, geologically and geographically. It must at the same time be admitted that the line of organic development has nowhere required for its advance the whole of the families comprehended in the two kingdoms, seeing that some of these are confined to one continent, and some to another, without a conceivable possibility of one having been connected with the other in the way of ancestry. The two great families of quadrumana, cebidæ and simiadæ, are a noted instance, the one being exclusively American, while the other belongs entirely to the old world. There are many other cases in which the full circular group can only be completed by taking subdivisions from various continents. This would seem to imply that, while the entire system is so remarkable for its unity, it has nevertheless been produced in lines geographically detached, these lines perhaps consisting of particular typical groups placed in an independent succession, or of two or more of these groups. And for this idea there is, even in the present imperfect state of our knowledge of animated nature, some countenance in ascertained facts, the birds of Australia, for example, being chiefly of the suctorial type, while it may be presumed that the observation as to the predominance of the useful animals in the Old World, is not much different from saying that the rasorial type is there peculiarly abundant. It does not appear that the idea of independent lines, consisting of particular types, or sets of types, is necessarily inconsistent with the general hypothesis, as nothing yet ascertained of the Macleay system forbids their having an independent set of affinities. On this subject, however, there is as yet much obscurity, and it must be left to future inquirers to clear it up.