ILLUSTRATIVE OF NATURAL SELECTION. 167 
it 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 facies 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 Papilionide. 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; 8. 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 
