The geographical distribution of animals, with a study of the relations ...

4 DISTRIBUTION OF ANIMALS. [part i.the soil, the aspect, or the vegetation, was adapted to them orthe reverse. The marshes, the heaths, the woods and forests,the chalky downs, the rocky mountains, had each their peculiarinhabitants, which reappeared again and again as we came totracts of country suitable for them. But as we got further awaywe began to find that localities very similar to those we hadleft behind were inhabited by a somewhat different set of species;and this difference increased with distance, notwithstandingthat almost identical external conditions might be often metwith. The first class of changes is that of stations ; the secondthat of habitats. The one is a local, the other a geograiihicalphenomenon. The whole area over which a particular animalis found may consist of any number of stations, but rarely ofmore than one habitat.Stations, however, are often so extensiveas to include the entire range of many species. Such are thegreat seas and oceans, the Siberian or the Amazonian forests,the North African deserts, the Andean or the Himalayanhighlands.There is yet another difference in the nature of the changewe have been considering. The new animals which we meetwith as we travel in any direction from our starting point, aresome of them very much like those we have left behind us,and can be at once referred to familiar types ; while othersare altogether unlike anything we have seen at home. Whenwe reach the Alps we find another kind of squirrel, in SouthernItaly a distinct mole, in Southern Europe fresh warblersand unfamiliar buntings. We meet also with totally newforms ;as the glutton and the snowy owl in Northern, the genetand the hoopoe in Southern, and the saiga antelope andcollared pratincole in Eastern Europe. The first series areexamples of what are termed representative species, the secondof distinct groups or types of animals. The one represents acomparatively recent modification, and an origin in or near thelocality where it occurs ; the other is a result of very ancientchanges both organic and inorganic, and is connected with someof theto discuss.most curious and difficult of the problems we shall have