10 Geographical Distribution of Animals. 



carried to an excess, and gave them a relation to the earth 

 which no other class, as a whole, holds to that degree, except, 

 perhaps, the insects, which are placed among the Articulata 

 in the same relation to the lower classes and the natural 

 element, which the class of birds maintains among Vertebrata. 

 The highest class of Vertebrata affords us examples of these 

 three modes of adaptation, the lowest of these being entirely 

 aquatic, and even absolutely marine ; next, we have fluvia- 

 tile types of the large terrestrial mammalia, in the family of 

 Manatees^ again, a swimming family among Carnivora, 

 another flying, most of them however walking upon their 

 four extremities on solid ground, but at the head of all, man, 

 standing upright, to look freely upwards, and to contemplate 

 the whole universe. 



This wonderful adaptation of the whole range of animals, 

 as it exists at present, shews the most intimate connection 

 with the order of succession of animals in former geological 

 periods. The four great types, Badiata, MoUusca, Articulata, 

 and Vertebrata, were introduced at the beginning simul- 

 taneously. However, the earliest representatives of these 

 great types were all aquatic. We find in the lowest beds 

 which contain fossils, Polypi^ together with star-fishes, bi- 

 valve shells, univalves, chambered shells, cases of worms, 

 and Crustacea, being representatives of at least seven out of 

 nine classes of invertebrate animals, if we are not allowed to 

 suppose that Mediisw existed also, and if insects were still 

 wanting for a time. But, in addition to these, fishes among 

 Vertebrata are introduced, but fishes only, all of which are 

 exclusively marine. At a somewhat later period insects come 

 in. We find next reptiles in addition to fishes — the lower 

 classes, or invertebrates, continuing to be represented through 

 all subsequent epochs, but by species changing gradually at 

 each period, as all classes do after they have been once intro- 

 duced. The first representatives among reptiles are marine, 

 next huge terrestrial ones, some, perhaps, flying types, and 

 with them, and perhaps even before them, birds, allied to 

 the wading tribes : still later, Mammalia, beginning again 

 with marine and huge terrestrial types, followed by the 



