4 DISTRIBUTION OF ANIMALS. [part i. 



the soil, the aspect, or the vegetation, was adapted to them or 

 the reverse. The marshes, the heaths, the woods and forests, 

 the chalky downs, the rocky mountains, had each their peculiar 

 inhabitants, which reappeared again and again as we came to 

 tracts of country suitable for them. But as we got further away 

 we began to find that localities very similar to those we had 

 left behind were inhabited by a somewhat different set of species; 

 and this difference increased with distance, notwithstanding 

 that almost identical external conditions might be often met 

 with. The first class of changes is that of stations ; the second 

 that of habitats. The one is a local, the other a geograiihical 

 phenomenon. The whole area over which a particular animal 

 is found may consist of any number of stations, but rarely of 

 more than one habitat. Stations, however, are often so extensive 

 as to include the entire range of many species. Such are the 

 great seas and oceans, the Siberian or the Amazonian forests, 

 the North African deserts, the Andean or the Himalayan 

 highlands. 



There is yet another difference in the nature of the change 

 we have been considering. The new animals which we meet 

 with as we travel in any direction from our starting point, are 

 some of them very much like those we have left behind us, 

 and can be at once referred to familiar types ; while others 

 are altogether unlike anything we have seen at home. When 

 we reach the Alps we find another kind of squirrel, in South- 

 ern Italy a distinct mole, in Southern Europe fresh warblers 

 and unfamiliar buntings. We meet also with totally new 

 forms ; as the glutton and the snowy owl in Northern, the genet 

 and the hoopoe in Southern, and the saiga antelope and 

 collared pratincole in Eastern Europe. The first series are 

 examples of what are termed representative species, the second 

 of distinct groups or types of animals. The one represents a 

 comparatively recent modification, and an origin in or near the 

 locality where it occurs ; the other is a result of very ancient 

 changes both organic and inorganic, and is connected with some 

 of the most curious and difficult of the problems we shall have 

 to discuss. 



