12 INTRODUCTION 



Again, both in Asia and in North America we have 

 vast areas of natural grassland forming weU-defined 

 Steppe areas, which possess a characteristic fauna. The 

 great mountain chains of the earth's surface are peopled 

 by faunas having certain special features, and the vast 

 area of coast-line which fringes the Arctic sea forms 

 a cold desert or tundra, whose fauna has many pecu- 

 liar features. As natural regions with a cold winter 

 chmate then, we have to consider (1) the Tundra, 

 (2) the Taiga or coniferous forest, (3) the Steppe, best 

 developed in the northern hemisphere, and (4) Mountain 

 regions. 



Where the temperature is permanently high, and 

 the precipitation great, we have (5) luxuriant Tropical 

 Forest, with its characteristic fauna, difiEering according 

 as the forest occurs in Africa, Asia, or South America, 

 but showing in aU cases certain special adaptations. 

 Again, in warm or tropical regions where the tempera- 

 ture is stiU high, but the rainfall small and unequally 

 distributed throughout the year, we have a thinning of 

 the forest into that type of grassland, or grassland 

 mingled with wood, which the botanists call Savana. 

 As the rainfall diminishes the savana thins out into 

 desert, so that we may conveniently consider (6) 

 Savanas and Warm Deserts together. 



This still leaves to be considered the fauna of (7) 

 Islands, which show some special features, and also the 

 animals of aquatic habitat, which we must consider 

 separately, according as they live (8) in the sea, or 

 (9) in fresh water. 



Such a scheme is obviously incomplete, in that it 

 does not cover the whole surface of the globe. It 

 omits, for example, any consideration of the fauna of 

 the deciduous forest which covers so much groiind in 



