and Pleiocene periods the Jordan basin formed the northernmost of a large system of fresh-water lakes, extending from north to south, of which, in the earlier part of the epoch, perhaps the Red Sea, and certainly the Nile Basin, the Nyanza, the Nyassa, and the Tanganyika lakes, and the feeders of the Zambezi, were members. During that warm period, a fluviatile ichthyological fauna was developed suitable to its then conditions, consisting of representative, and perhaps frequently identical species, throughout the area under consideration.
"The advent of the glacial period was, like its close, gradual. Many species must have perished under the change of conditions. The hardiest survived, and some perhaps have been gradually modified to meet those new conditions. Under this strict isolation it could hardly be otherwise; and however severe the climate may have been, that of the Lebanon, with its glaciers probably corresponding with the present temperature of the Alps at a proportional elevation (regard being had to the difference of latitude), the fissure of the Jordan being, as we certainly know, as much depressed below the level of the ocean as it is at present; there must have been an exceptionally warm temperature in its waters in which the existing ichthyological fauna could survive."
Such facts as these tell us that Palestine is not to be regarded as a European country, but rather as an African outlier, while it has also strong affinities with Asia, as proved by others of these fishes. In fact, it stands in the midst between three continents, and is, in a very important sense, the centre of the world. Dr Tristram, our best authority in this department, shows us how Palestine contains an epitome of the life of the world, and does so just because it includes almost every variety of climate.
Linnæus said that we know more of the botany and zoology of farther India than we do of those of Palestine.
