160 THE MALAYAN PAPILIONIDM AS 



5. Race or subspecies. These are local forms com- 

 pletely fixed and isolated ; and there is no possible test 

 but individual opinion to determine which of them shall 

 be considered as species and which varieties. If sta- 

 bility of form and " the constant transmission of some 

 characteristic peculiarity of organization " is the test of 

 a species (and I can find no other test that is more 

 certain than individual opinion) then every one of 

 these fixed races, confined as they almost always are 

 to distinct and limited areas, must be regarded as a 

 species ; and as such I have in most cases treated them. 

 The various modifications of Papilio Ulysses, P. Peran- 

 thus, P. Codrus, P. Eurypilus, P. Helenus, &c., are 

 excellent examples; for while some present great and 

 well-marked, others offer slight and inconspicuous dif- 

 ferences, yet in all cases these differences seem equally 

 fixed and permanent. If, therefore, we call some of 

 these forms species, and others varieties, we introduce a 

 purely arbitrary distinction, and shall never be able to 

 decide where to draw the line. The races of Papilio 

 Ulysses, for example, vary in amount of modification 

 from the scarcely differing New Guinea form to those 

 of Woodlark Island and New Caledonia, but all seem 

 equally constant ; and as most of these had already 

 been named and described as species, I have added the 

 New Guinea form under the name of P. Autolycus. 

 We thus get a little group of Ulyssine Papilios, the 

 whole comprised within a very limited area, each one 

 confined to a separate portion of that area, and, though 

 differing in various amounts, each apparently constant. 



