ILLUSTRATIVE OF NATURAL SELECTION. 167 



ifc is true, are acquainted with the influences of climate, 

 altitude, and other physical conditions, in modifying 

 the forms and external characteristics of plants ; but 

 I am not aware that any peculiar influence has been 

 traced to locality, independent of climate. Almost 

 the only case I can find recorded is mentioned in 

 that repertory of natural-history facts, " The Origin 

 of Species," viz. that herbaceous groups have a ten- 

 dency to become arboreal in islands. In the animal 

 world, I cannot find that any facts have been pointed 

 out as showing the special influence of locality in 

 giving a peculiar fades to the several disconnected 

 species that inhabit it. What I have to adduce on 

 this matter will therefore, I hope, possess some in- 

 terest and novelty. 



On examining the closely allied species, local forms, 

 and varieties distributed over the Indian and Malayan 

 regions, I find that larger or smaller districts, or even 

 single islands, give a special character to the majority 

 of their Papilionidse. For instance : 1. The species 

 of the Indian region (Sumatra, Java, and Borneo) 

 are almost invariably smaller than the allied species 

 inhabiting Celebes and the Moluccas ; 2. The species 

 of New Guinea and Australia are also, though in a 

 less degree, smaller than the nearest species or va- 

 rieties of the Moluccas ; 3. In the Moluccas them- 

 selves the species of Amboyna are the largest; 4. 

 The species of Celebes equal or even surpass in size 

 those of Amboyna; 5. The species and varieties of 

 Celebes possess a striking character in the form of 



