4. Distribution: This is the term applied to the phenomena exhibited by the presence of different organisms in different localities of the globe; or, as Mr. Spencer phrases it, "the phenomena of distribution in space." These phenomena are very various. Sometimes, it is said, we find adjacent territories, with similar conditions, occupied by quite different faunas. In other regions, we find closely allied faunas in areas remote from each other in latitude, and contrasted in both soil and climate. The reasoning, as given by Mr. Darwin and adopted by Mr. Spencer, is this: that "as like organisms are not universally or even generally found in like habitats, nor very unlike organisms in very unlike habitats, there is no predetermined adaptation of the organisms to the habitats." "In other words," Mr. Spencer adds, "the facts of distribution in space do not conform to the hypothesis of design." The reason why they do not is claimed to be that there are impassable barriers between the similar areas which are peopled by dissimilar forms; whereas there are no such barriers between the dissimilar areas which are peopled by dissimilar forms. The conclusion is, "that each species of organism tends ever to expand its sphere of existence--to intrude on other areas, other modes of life, other media." That is to say, there is a constant competition among races of organisms for possession of the fields in which they can find the means of subsistence and expansion; and this leads to new modes of existence, new media of life, new structures and new habitats. The reader can now retrace his steps, and advert to the facts that are relied upon, under the four heads of the argument: