OF THE MALAYAN REGION. 17 
1. Eronia tritea . . . . . compared with Eronia Valeria (Java). 
2. Iphias Glaucippe, var. . . » »  Iphias Glaucippe (Java). 
3. Pieris Zebuda . . eis = » Pieris Descombesi (India). 
a, Po TOR 2. . es Fi » P. Nero (Malacca). 
D a hh. Suns eee ee M a » P. Hyparete (Java). 
5 E oe | have the same form, but are isolated species. 
8. P. Eperia, Bd. . . . . . compared with P. Coronis (Java). 
Ce. M S... o sue uA » » P.,n.s. (Malacca). 
I Ss kf d » P. Tilaha (Java). 
The other species of Terias, one or two Pieris, and the genus Callidryas do not exhibit 
any perceptible change of form. | 
In the other families there are but few similar examples. The following are all that I 
can find in my collection :— 
Cethosia Hole . . . . . . . . compared with Cethosia Biblis (Java). 
Jünonia, n. B +: Uc coto wt a " » Junonia Polynice (Borneo). 
Limenitis Limite. oc... 5... sn. +: - » Limenitis Procris (Java). 
Cynthia Arsinoë, var. . . i jj » Cynthia Arsinoë (Java, Sum., Born.). 
All these belong to the family of the Nymphalidæ. Many other genera of this family, as 
Diadema, Adolias, Charaxes, and Cyrestis, as well as the entire families of the Danaidæ, 
Satyridæ, Lycænidæ, and Hesperidæ, present no examples of this peculiar form of the 
upper wing in the Celebesian species. 
The facts now brought forward seem to me of the highest interest. We see that 
almost all the species in two important families of the Lepidoptera ( Papilionidæ and 
 Pieridæ) acquire, in a single island, a characteristic modification of form distinguishing 
them from the allied species and varieties of all the surrounding islands. In other 
equally extensive families no such change occurs, except in one or two isolated species. 
However we may account for these phenomena, or whether we may be quite unable to 
account for them, they furnish, in my opinion, a strong corroborative testimony in favour 
of the doctrine of the origin of species by successive small variations; for we have here 
slight varieties, local races, and undoubted species, all modified in exactly the same 
manner, indicating plainly a common cause producing identical results. On the gene- 
rally received theory of the original distinctness and permanence of species, we are met 
by this diffculty : one portion of these curiously modified forms are admitted to have 
been produced by variation and some natural action of local conditions; whilst the other 
portion, differing from the former only in degree, and connected with them by insensible 
gradations, are said to have possessed this peculiarity of form at their first creation, or to 
have derived it from unknown causes of a totally distinct nature. Is not the à priori 
evidence in favour of the assumption of an identity of the causes that have produced 
such similar results ? and have we not a right to call upon our opponents for some proofs 
of their own doctrine, and for an explanation of its difficulties, instead of their assuming 
that they are right, and laying upon us the burthen of disproof ? 
Let us now see if the facts in question do not themselves furnish some clue to their 
VOL. XXV. à D 
