338 Mr. A. Radcliffe Grote on the Changes in the 
like thickening of the costa at the base, which I desig- 
nate, after Comstock, as vein 1., for the reason that I am 
disposed to consider it, together with all thickenings of 
the tegument, as homologous with the other veins.* 
Hiven if another derivation for it were established, its 
existence might still be indicated by a number. 
If, now, we review the venation of the butterflies in 
search of features which shali throw light upon the phylo- 
geny of the group, and prove available for the purposes 
of taxonomy, it is clear that secondary characters must 
be set aside in the endeavour to find those which are 
primary in their nature. It must be borne in mind that 
this distinction is a relative and not an absolute one, and 
that here as elsewhere our conception of the value of any 
character changes with the extent of ourinformation. A 
scheme of classification is therefore the measure of the 
acquaintance, or non-acquaintance, of the classifier with 
his subject. Classification itself becomes a possible field 
for psychical activity, solely by reason of the differen- 
tiation which has attended biological development, and 
has arisen through the interaction of the organism and 
the conditions permitting its existence. In a study of the 
wings of all the families of the butterflies, I have been 
able to rely only upon the aforesaid characters offered by 
the abbreviated veins below vein vii. on the primaries, 
which allow us to distinguish the Parnassiidee and Papi- 
lionides from the rest of the butterflies, including the 
Hesperide. The remarkably distinct feature of the 
appearance of vein ix. upon the forewings of the Swallow- 
tails and their allies leads me to consider it of both 
phylogenetic and taxonomic import, and as indicating a 
common origin for the series of forms exhibiting it, 
which is separate from that of the remaining day-flying 
Lepidoptera; it seems to be of subprimary value. 
Furthermore, I have persuaded myself from the data 
* “Tt has been shown by Hagen that the two layers of mem- 
brane can be separated when the wings are recently formed, and it 
is then seen that each layer is traversed by lines of harder matter, 
the nervures. These ribs are frequently called wing-veins, or 
nerves, but as they have no relation to the anatomical structures 
bearing those names, it is better to make use of the term 
nervures.”—Ent. Record, 1896, p. 231. For the purposes of the 
present paper it has seemed to me clearer and shorter to use the 
common term. 
