222 VIEWS OF NATURE. 



ther of animals or plants, are determined by laws with which 

 we are still unacquainted. In each of the great divisions of 

 the animal kingdom, as insects, reptiles, Crustacea, birds, 

 fishes, or mammalia, the dimensions of the body oscillate 

 between certain extreme limits. But these limits, based on 

 the observations hitherto contributed to science, may be en- 

 larged by new discoveries of species with which we are at 

 present unacquainted. 



In land animals a high degree of temperature, depending on 

 latitude, appears to have exercised a favourable influence on 

 the genetic development of organization. Thus the small and 

 slender form of our lizards expands in the south into the 

 colossal, unwieldy, and mail-clad body of the formidable croco- 

 dile. In the huge cats of Africa and America, the tiger, 

 lion, and jaguar, we find, repeated on a larger scale, the 

 form of one of the smallest of our domestic animals. But if 

 we penetrate into the recesses of the earth, and search the 

 tombs of plants and animals, the fossil remains thus brought 

 to light not only manifest a distribution of forms at variance 

 with the present climates, but they also reveal colossal struc- 

 tures, which exhibit as marked a contrast with the small types 

 that now surround us, as does the simple yet dignified 

 heroism of the ancient Greeks, when compared with what is 

 recognized at the present day as " greatness of character." 

 If the temperature of the earth has undergone considerable, 

 perhaps periodically recurring changes, and, if even the 

 relations between sea and land, and the height and pres- 

 sure of the atmospheric ocean (14), have not always been the 

 same, then the physiognomy of nature, and the magnitude 

 and forms of organic bodies, must also have been subject 

 to many variations. Enormous Pachydermata, elephantine 

 Mastodons, Owen's Mylodon robustus, and the Colossochelys,-* 

 a land tortoise upwards of six feet in height, once inhabited 

 forests of colossal Lepidodendra, cactus-like Stigrnaria3, and 



* Fossil remains of this gigantic antediluvian tortoise are now in the 

 British Museum. ED. 



