OF THE MALAYAN REGION. 17 



1. Eronia tritaea compared with Eronia Valeria (Java). 



2. Iphias Glaucippe, var. . . „ „ Iphias Glaucippe (Java). 



3. Pieris Zebuda „ „ Pieris Descombesi (India). 



4. P. Zarinda „ » P- Nero (Malacca). 



5. P., n. s „ „ P. Hyparete (Java). 



6. P. Hombronii . 



, have the same form, but are isolated species. 



7. P. Ithome ... J 



8. P. Eperia, Bd compared with P. Coronis (Java). 



9. P. Polisma „ „ P., n. s. (Malacca). 



10. Terias, n. s „ „ P- Tilaha (Java). 



The other species of Terim, 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 aU that I 

 can find in my collection : — 



Cethosia ^ole compared with Cethosia Biblis (Java). 



Junonia, n. s „ „ Junonia Polynice (Borneo). 



Limenitis Limire „ „ Limenitis Procris (Java). 



Cynthia Arsinoe, var „ „ Cynthia Arsinoe (Java, Sum., Born.). 



AU these belong to the family of the XymphaUdae. Many other genera of this family, as 

 Diadema, Adolias, Charaxes, and Cyrcstis, as weU as the entire families of the Danaidae, 

 Satyridse, Lyccenidse, and Hesperidse, 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 (Papilionidae and 

 Pieridae) acquire, in a single island, a characteristic modification of form distinguishing 

 them from the allied species and varieties of aU the sui-rounding islands. In other 

 equaUy extensive famUies 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 smaU variations ; for we have here 

 sUght varieties, local races, and imdoubted species, all modified in exactly the same 

 manner, indicating plainly a common cause producing identical results. On the gene- 

 raUy received theory of the original distinctness and permanence of species, we are met 

 by this diflS-Culty : one portion of these curiously modified forms are admitted to have 

 been produced by variation and some natural action of local conditions ; whUst 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 theu' first creation, or to 

 have derived it from unknown causes of a totaUy distinct nature. Is not the a j^riori 

 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 difl&culties, instead of their assuming 

 that they are right, and laying upon us the biu-then of disproof ? 



Let us now see if the facts in question do not themselves furnish some clue to their 



VOL. XXV. D 



