142 THE MALAYAN PAPILIONIDE AS 
tinguished by very slight characters, but in most 
cases so constant in large series of specimens, and 
so easily separable from each other, that I know not 
on what principle we can refuse to give them the 
name and rank of species. One of the best and most 
orthodox definitions is that of Pritchard, the great 
ethnologist, who says, that “‘ separate origin and dis- 
tinctness of race, evinced by a constant transmission of 
” consti- 
tutes a species. Now leaving out the question of 
“ origin,” which we cannot determine, and taking 
only the proof of separate origin, ‘ the constant trans- 
some characteristic peculiarity of organization,’ 
mission of some characteristic peculiarity of organiza- 
tion,” we have a definition which will compel us to 
neglect altogether the amount of difference between 
any two forms, and to consider only whether the dif- 
ferences that present themselves are permanent. The 
rule, therefore, I have endeavoured to adopt is, that 
when the difference between two forms inhabiting 
separate areas seems quite constant, when it can be 
defined in words, and when it is not confined to a 
single peculiarity only, I have considered such forms 
to be species. When, however, the individuals of . 
each locality vary among themselves, so as to cause 
the distinctions between the two forms to become 
inconsiderable and indefinite, or where the differences, 
though constant, are confined to one particular only, 
such as size, tint, or a single point of difference in 
marking or in outline, I class one of the forms as a 
variety of the other. 
