GEOGRAPHICAL DISTRIBUTION OF ANIMALS 1557 



The humming-birds are peculiar to the western 

 continent, and in the tropical regions of America 

 various birds of the most glittering plumage, to- 

 gether with numberless fire-flies, lend an almost 

 magical charm to the aspect of nature. The range 

 of the humming-birds extends over the whole con- 

 tinent to the southward of the 42d parallel (north 

 lat.) and stretches upon the western side of North 

 America as high as the parallel of 60 an evidence 

 of the superior warmth which distinguishes that side 

 of the American continent. 



Both reptiles and insects are abundant in the New 

 World, which, owing to its excessive moisture and 

 dense vegetation, is peculiarly suited to the develop- 

 ment of these departments of the natural kingdom. 

 Venomous serpents are more numerous in tropical 

 America than in any other part of the globe. The 

 rattlesnake occurs in both divisions of the continent, 

 within the parallels of 44 to the northward and of 30 

 to the south of the equator ; the huge boa-constrictor, 

 the largest of the serpent tribe, and the terror even 

 of the natives, dwells in the marshes and swamps of 

 South America. Huge caymans, iguanas, and other 

 lizards, with numberless alligators and water-snakes, 

 abound in the rivers and temporary lagoons of the 

 same region. 



Australia possesses a zoology which is more dis- 

 tinctive than that of any other part of the world. Its 

 native insects, reptiles, birds, and land animals are 

 all strikingly different from those of other regions. 

 The difference is greatest (or, at any rate, most ob- 

 vious to ordinary observation) in the case of its land 



