Structure of the Wings of Butterflies. 559 
observed that all contention as to forms occupying a 
higher or lower position in a linear series is to a great 
extent illusory, since specialization proceeds unequally ; 
and it has been from practical considerations that I have 
adhered to the Linnean arrangement. Moreover, my 
scheme is' accompanied by a synopsis of the grades of 
specialization presented by the venation of the different 
groups which authors have proposed. 
The attempt to find distinctive characters of venation 
for all the suggested families has so far failed as to render 
the tabular arrangement presented here of only partial 
use as a guide to the recognition of the forms it contains. 
Before offering it I shall attempt to render the subject 
5 
more lucid by classifying in a brief summary of the 
families the characters upon which I lay stress. 
Fam. Parnassup®, In the Parnassiine, the more 
specialized subfamily, the radius is four-branched 
(111j 4.9, Ils, 1114, 5), the cell remains closed, the upper 
median branch (iv;) has left its more generalized position 
on the cross-vein and emerges from the radius without the 
cell, the middle branch (vein iva) has become cubital in 
position on both wings, whilst on the secondaries vein vii. 
has become shortened. In the Thainz the radius is 
in a more generalized state, being 5-veined ; vein iv; 
spring's from the cross-vein very near the radius, the cell is 
closed, and vein vii. of the secondaries is_ less 
abbreviated. 
Fam. Paritionip#. More generalized than the Par- 
nassiide. The radius is 5-veined, the furcation of 
veins ii, and i; is longer than in the preceding; 
vein iy; is removed from the radius, vein ivg has a median 
generalized position on the primaries whilst on the 
secondaries it inclines towards the cubitus ; the cells are 
strongly closed and vein vu. of the hindwings is more 
developed than in the Parnassude. 
In contrasting the characters of this with those of the 
succeeding series, the Parnassudee and _ Papilionide 
(Papilionides, auct.) are seen to be more specialized in the 
absence of vein vill on the secondaries, while the absorp- 
tion of vein ilig in the Parnassiide is a convergent 
character which we meet with again in the Pieridz and 
Lyceenide. Their generalized condition is evidenced by 
the presence of vein ix. on the primaries, and in the 
Papilionidz, by the position of vein iv, on the same wings. 
