ig8 FOOT-NOTES TO EVOLUTION. 



life, though gradual, to be more rapid. The barrier of 

 frost which keeps the fauna of the tropics from en- 

 croaching on the northern regions once crossed, we 

 come to the multitude of animals whose life depends on 

 sunshine, the characteristic forms of the neotropical 

 realm. 



The neotropical realm includes South America, the 



West Indies, and the hot coast lands of Mexico and 



Central America. To the northward this 



eo ropica realm overlaps the holarctic in the tran- 



realm. . . . ' 



sition regions of Sonora, Arizona, Texas, 



and Florida; but to the southward the barrier of the 



broad ocean keeps it practically distinct from all others. 



The richness of this fauna in forms and species makes 



the great forests of the Amazon the dream of the 



naturalist. Joaquin Miller gives a vivid picture of the 



life of tropical America: 



" Birds hung and swung, green-robed and red, 

 Or drooped in curved lines dreamily, 

 Rainbows reversed from tree to tree ; 

 Or sang, low hanging overhead, 

 Sang soft as if they sang and slept, 

 Sang low like some far waterfall, 

 And took no note of us at all." 



Corresponding to the neotropical realm in position, 



but with a less rich and varied fauna, is the Ethiopian 



realm. This includes the greater part 

 Ethiopian realm. , . , . j n i 



of Africa, merging gradually on the 



north into the holarctic realm, through the transition 

 regions of Barbary, Italy, and Spain. In monkeys, her- 

 bivorous animals, and reptiles, this region is wonderfully 

 rich. In variety of birds and fishes the neotropical 

 region far surpasses it. 



The Indian realm comprises southern Asia and the 

 neighbouring islands. Its rich fauna has much in com- 



