12 OX THE LAW WHICH HAS REGULATED 



recent mountain elevations, separates faunas and floras 

 which scarcely differ more than may be due to climate 

 and latitude alone. 



The series of facts alluded to in Proposition (3), 

 of closely allied species in rich groups being found 

 geographically near each other, is most striking and 

 important. Mr. Lovell Reeve has well exemplified it 

 in his able and interesting paper on the Distribution 

 of the Bulimi. It is also seen in the Humming- 

 birds and Toucans, little groups of two or three 

 closely allied species being often found in the same 

 or closely adjoining districts, as we have had the 

 good fortune of personally verifying. Fishes give 

 evidence of a similar kind : each great river has 

 its peculiar genera, and in more extensive genera 

 its groups of closely allied species. But it is the 

 same throughout Nature ; every class and order of 

 animals will contribute similar facts. Hitherto no 

 attempt has been made to explain these singular 

 phenomena, or to show how they have arisen. Why 

 are the genera of Palms and of Orchids in almost 

 every case confined to one hemisphere ? Why are 

 the closely allied species of brown-backed Trogons all 

 found in the East, and the green-backed in. the 

 West? Why are the Macaws and the Cockatoos 

 similarly restricted ? Insects furnish a countless 

 number of analogous examples ; the Goliathi of 

 Africa, the OrnithopteraB of the Indian Islands, the 

 Heliconidse of South America, the DanaidaB of the 

 East, and in all, the most closely allied species found 



