48 THE PRESENT. 



covered, enabling the palaeontologist to unfold the relations 

 of fossil plant-life, its distribution in space, and its progress 

 in time, even as the botanist now determines its existing 

 relationships, and maps out its centres and areas of geo- 

 graphical arrangement. 



2. ITS FAUNA OR ANIMAL LIFE. 



As with plants, so with animals. While Ave find them 

 everywhere on the earth, in the air, and in the waters 

 on the substances of plants, and even in the living tissues 

 of other animals they are as imperatively governed by the 

 influences of climate, food, and other external conditions as 

 the Vegetable world, though possessed for the most part of 

 a locomotion which at first sight might seem to confer on 

 them an ubiquity of habitat. Thus, the FAUNA of the 

 tropics is essentially different from that of the temperate 

 zone, and the animals which people the temperate zone 

 have but little in common with those of the arctic regions. 

 It is true that some, like Man and his companions, the 

 dog, horse, and other domesticated animals, have a range all 

 but universal ; but generally speaking, the zones of Animal 

 Life horizontally and vertically are about as sharply 

 defined as those of vegetation. The elephant and rhinoceros 

 that luxuriate in the low tropical jungle would fare but in- 

 differently on the lofty slopes of the Himalayas ; while the 

 buffalo and bison which herd at these heights would cease 

 to exist were they raised but a few thousand feet higher. 

 As with altitude on land, so with depth in the ocean ; and 

 thus the sea- weeds and shells that grow and live within the 

 influence of the tides constitute a Littoral zone very different 

 from the Laminarian or broad sea-tangle zone which extends, 

 in British seas, from 40 to 90 feet in depth ; this again is 



